Protocol for the Open Sky School: a two-arm clustered randomized controlled trial to test the effectiveness of a nature-based intervention on mental health of elementary school children
《Open Sky School 协议：一项双臂整群随机对照试验，用于测试基于自然的干预对小学儿童心理健康的有效性》

Abstract

Background

This article outlines the protocol for a trial to test the effectiveness of a nature-based intervention called Open Sky School to reduce mental health problems among elementary school children. Experimental studies show that contact with nature (e.g. walks in parks) improve mental health. A growing number of teachers have been applying outdoor education within the regular school curriculum and evidence suggests that such teaching methods could improve students’ mental health but a randomized controlled trial has never been conducted.

Methods

A two-arm clustered randomized controlled trial will be conducted in elementary schools across Québec, Canada. Following informed consent by teachers, parents and students, schools will be randomly assigned 1:1 to the intervention or the control group with a total of 2500 5-6^th grade students and 100 teachers expected to participate. The intervention will take place outdoors in a green-space (2 h per week for 12 weeks) and include a toolkit of 30 activities to foster well-being (e.g. mindfulness) and academic competencies (e.g. mathematics). Questionnaires will be administered to teachers and students before, immediately after and 3 months after the intervention. The primary outcome will be reductions of mental health problems in children from pre-to-post test (Social Behavior Questionnaire: self and teacher reports). Secondary outcomes include depression, positive and negative affect, nature connectedness, and pro-environmental behaviors among children. We will explore, immediate benefits on teacher’s well-being and positive and negative affect and sustained benefits among students at 3 months follow-up. For the primary outcome, we will explore moderators including child’s sex, child’s disability status, the green-space of neighbourhoods, the school’s socio-economic position and teacher’s experience.

Discussion

In conducting the first randomized controlled trial of the Open Sky School, our results could provide empirical evidence on the effectiveness of nature-based interventions in reducing mental health problems among elementary school children.

Trial registration

This study was registered with clinicaltrials.gov: NCT05662436 on December 22, 2022.

Background

Mounting evidence indicates that spending time in nature can be beneficial for mental health for individuals of all ages (e.g., to reduce symptoms of depression and anxiety) [1,2,3,4]. Indeed, large epidemiological studies have reported an association between residing in an area with a high density of green vegetation and mental health. For instance, a recent Danish study including over 900,000 children suggested that proximity to green space in childhood was associated with a lower onset of psychiatric disorders later in life, independently from other known risk factors such as the family socioeconomic status and parents’ psychopathology [5]. A double-blind, controlled, within-subject study carried out among children aged 7 to 12 years diagnosed with attention-deficit/hyperactivity disorder also suggested that walks lasting 20 min in urban parks reduced sustained attention difficulties more than walking in town or in the streets around their residence [6]. Large effect sizes were observed (0.52 and 0.77 respectively), which were comparable to the effect of psychostimulant medication. In addition to health benefits, spending time in nature during childhood is known to increase nature connectedness and pro-environmental attitudes and behaviors. This would be because when children spend time enjoying nature, they tend to feel more connected to the environment and become more likely to engage in behaviors to protect it as a result e.g. recycling, volunteering for pro-environmental causes [7]. As such, increasing time spent in nature at school could be a highly accessible way cultivate children’s pro-environmental attitudes and behaviors while also reducing mental health problems. Accessible interventions capable of reducing mental health problems in children are also particularly timely given numerous reports suggesting worsening levels of mental health among youth since the beginning of the COVID-19 pandemic [8] and increasing preoccupations for climate change among youth [9]. While the practice of outdoor education (e.g. teaching the standard curriculum off campus) has been increasingly encouraged in education, including in Canada, where a rising number of teachers practice outdoor education [10], the effectiveness of such practices in reducing mental health problems has never been tested with a robust randomized-control trial design.
越来越多的证据表明，在自然环境中度过时间对各个年龄段人群的心理健康都有益（例如，可以减轻抑郁和焦虑症状）[1, 2, 3, 4]。事实上，大规模的流行病学研究已经报告了居住在高绿化密度地区的关联性与心理健康。例如，一项最近发表在丹麦的研究包括超过 90 万名儿童，表明童年时期接近绿地与成年后精神疾病的发生率降低相关，且这种关联独立于其他已知风险因素，如家庭社会经济地位和父母的精神病理学[5]。一项在 7 至 12 岁被诊断为注意力缺陷/多动障碍的儿童中进行的双盲、对照、自身前后对照研究也表明，在城市公园中持续 20 分钟的散步比在城镇或居住地周围的街道上行走更能减少持续注意力困难[6]。观察到较大的效应量（分别为 0.52 和 0.77），这些效应与精神兴奋剂药物的效果相当。 除了健康益处外，儿童时期在自然中度过时光还能增强与自然的联系以及亲环境态度和行为。这是因为当儿童在享受自然时，他们往往会感觉更与环境联系紧密，从而更可能参与保护环境的行动，例如回收、为亲环境事业做志愿者[7]。因此，增加学校中在自然中度过的时间可能是一种非常便捷的方式，既能培养儿童的亲环境态度和行为，又能减少心理健康问题。鉴于自 COVID-19 大流行开始以来，众多报告显示青年心理健康水平恶化[8]，以及青年对气候变化日益关注[9]，能够减少儿童心理健康问题的可及性干预措施尤其及时。 尽管户外教育（例如在校外教授标准课程）在教育领域（包括加拿大，越来越多的教师实践户外教育[10]）中越来越受到鼓励，但这种实践在减少心理健康问题方面的有效性从未通过严谨的随机对照试验设计进行过测试。

We are nevertheless aware of two quasi-experimental studies that tested the effectiveness of education outside the classroom applied directly within the school curriculum in reducing mental health problems among students. The first study was carried out in Sweden with children aged 6 to 12 years (n = 230) and used a non-equivalent quasi-experimental design to assess whether daily teaching outside (e.g., in the schoolyard) for 6 months reduced symptoms of mental disorders, in comparison with usual indoor education. The intervention entailed one hour per day of outdoor education where children were taught academic competencies while being outside and manipulating elements of nature (e.g., branches and stones used to represent mathematical concepts rather than textbooks). Findings suggested a significant reduction in internalized and externalized symptoms pre-to-post intervention, but only among boys [11]. A second quasi-experimental study was conducted over the course of a school year with students aged 9 to 11 years (n = 631) and aimed in part to assess the benefits of outdoor teaching on mental health, in comparison to education as usual. The authors found that pro-social behaviors improved among all children and that hyperactivity and problems with peers were reduced among disadvantaged children [12]. However, quasi-experimental designs do not use randomization and conclusions about causal associations between the intervention and outcomes are limited. Further, the two quasi-experimental studies described above did not require that the outdoor education take place in a green space. Therefore, the effectiveness of education outside of the classroom that necessarily includes the component of exposure to nature in reducing mental health problems needs further investigation. In light of the available empirical evidence and the aforementioned limitations, we propose to test the effectiveness of a nature-based intervention implemented within the school context in reducing mental health problems in children, increasing their pro-environmental attitudes and behaviors as well as improving teachers’ well-being. Our intervention program will essentially entail 5-6^th grade teachers taking their students outside to a nearby green space (e.g. park, wooded area) during school hours for 2 h a week for 12 weeks. The teachers will be provided with a toolkit of outdoor lesson plans that were professionally designed to improve mental health and develop classic academic competencies.
尽管如此，我们仍了解到两项准实验研究，这些研究测试了在课堂教学之外直接应用于学校课程中的教育方式对减少学生心理健康问题的有效性。第一项研究是在瑞典进行的，针对 6 至 12 岁的儿童（n = 230），采用非等效准实验设计，评估每天在户外（例如在学校操场）进行 6 个月的教学是否能够减少精神疾病症状，与常规室内教育进行比较。该干预措施包括每天一小时的户外教育，孩子们在户外学习学术能力，同时操作自然元素（例如，用树枝和石头来代表数学概念，而不是教科书）。研究结果表明，干预前后，内部化和外部化症状均有显著减少，但仅限于男孩[11]。第二项准实验研究是在一个学年期间进行的，针对 9 至 11 岁的学生（n = 631），旨在部分评估户外教学对心理健康的好处，与常规教育进行比较。 作者发现所有儿童的社会行为都有所改善，而弱势儿童的多动症和同伴问题有所减少[12]。然而，准实验设计不使用随机化，因此干预措施与结果之间的因果关系结论有限。此外，上述两个准实验研究并未要求户外教育必须在绿色空间进行。因此，需要进一步研究在课堂外进行的、必然包含接触自然成分的教育，在减少心理健康问题方面的有效性。鉴于现有的实证证据和上述局限性，我们建议在校园环境中测试基于自然的干预措施在减少儿童心理健康问题、提高其环保态度和行为以及改善教师福祉方面的有效性。我们的干预计划将包括 5-6 名五、六年级教师在 12 周内，每周用 2 小时将学生带到附近的绿色空间（例如公园、林地）进行户外活动。 教师将获得一套户外教案工具包，这些教案由专业人士设计，旨在改善心理健康和发展经典学术能力。

Our main objective is to test the effectiveness of the Open Sky School, a nature-based school intervention, designed to decrease mental health problems in children, immediately after the intervention. We hypothesize that the Open Sky School will lead to greater reductions in overall mental health problems in children in comparison to a control group (primary outcome), in addition to greater improvements in children’s symptoms of depression, affect, connectedness to nature and pro-environmental behaviors and attitudes immediately after the intervention (secondary outcomes). We will explore whether the intervention improves teachers well-being and affect, and if benefits in primary and secondary outcomes are maintained at 3 months follow-up among children. We will also explore potential moderators in the association between exposure to the program and outcomes including the children’s sex [11, 13] and disability status [6], the quality of green-space surrounding school [14], the deprivation indicator of the school [12] and the amount of experience of teachers [15].
我们的主要目标是测试 Open Sky School 的自然学校干预措施的有效性，该措施旨在减少儿童在干预后的心理健康问题。我们假设与 对照组相比，Open Sky School 将导致儿童整体心理健康问题更大的减少（主要结果），以及在干预后儿童抑郁症状、情感、与自然的联系和亲环境行为及态度方面有更大的改善（次要结果）。我们将探讨干预是否改善了教师福祉和情感，以及主要和次要结果在儿童 3 个月随访中是否得到维持。我们还将探讨项目暴露与结果之间的潜在调节因素，包括儿童的性别[11,13]、残疾状况[6]、学校周边绿地质量[14]、学校的剥夺指标[12]以及教师经验量[15]。

Method and design  方法和设计

Participants  参与者

Eligibility criteria  纳入标准

Participating schools will be recruited from a list of 280 French language elementary schools in the Canadian province of Quebec, enrolled in a larger study conducted by the Observatory for Children’s Education and Health, which aims to document the consequences of the COVID-19 pandemic on 4^th grade children’s academic achievement (www.observatoireenfants.ca/en). Additional inclusion criteria for schools are: (a) approval by their school board, (b) access to a natural environment (e.g., park, wooden area) on school grounds or within 1 km of the school and (c) having 5-6^th grade teachers provide informed and written consent to participate in this study (see Appendix 1). Inclusion criteria for children to participate in assessments are (a) enrollment in 5-6^th grade, (b) providing their assent (see Appendix 2) and (c) having their parents or legal guardians provide informed written consent (see Appendix 3). As indicated on the information and consent form, participants can withdraw from the study at any time.
参与学校将从魁北克省（加拿大）280 所法语小学名单中招募，这些学校已参与由儿童教育与健康观察站进行的一项更大规模的研究，该研究旨在记录 COVID-19 大流行对四年级学生学业成就的影响（www.observatoireenfants.ca/en）。学校纳入的额外标准包括：(a) 经校务委员会批准，(b) 学校校园内有自然环境（例如公园、林地）或距离学校 1 公里范围内有自然环境，以及(c) 有 5-6 名四年级教师提供知情同意书参与本研究（见附录 1）。儿童参与评估的纳入标准包括：(a) 注册为五、六年级学生，(b) 提供其同意（见附录 2），以及(c) 其父母或法定监护人提供知情同意书（见附录 3）。如信息与同意书所示，参与者可随时退出研究。

Intervention group  干预组

The intervention aims to provide approximately 2 h of exposure to nature per week and access to a toolkit of pedagogical and mental health activities grounded in positive psychology. The rationale for Open Sky School was informed by the growing literature on the benefits of spending time in nature for mental health [1]. The exposure to nature consists of teachers bringing their students to the highest quality green space within 1 km of a school which could be located on or off campus. For instance, this could be a forest on campus or a park nearby. The class will spend a total of 2 h (i.e. 2 one hour visits or one 2 h visits) per week for 12 weeks (transportation included), which is in line with recent guidelines recommending a minimum of 2 h per week in nature [16]. As summarized in Table 1, the main component of the Open Sky School consists of exposing children to nature, which is embedded in various activities (academic and mental health components), while providing teacher training and support. To this end, we designed an online toolkit of pedagogical and mental health activities. The mental health activities are rooted in positive psychology (mindfulness, philosophy for children and art therapy) and are designed to improve children’s mental health [17]. The pedagogical activities (French language, mathematics and sciences) are aligned on the core academic learning competences required by the Ministry of Education of Québec. Teachers will be allowed to use their own pedagogical activities (if they do, they will be asked to describe their activities), but are encouraged to use those provided in the toolkit, because they were professionally designed and positively appraised in the quality assessment phase. Nevertheless, as our trial primarily aims to reduce mental health problems among children, teachers will be required to carry out at least 10 mental health activities provided in the toolkit. The toolkit also includes brief video-based modules on best practices for implementing mental health activities outdoors (i.e., how to deal with negative emotions; how children can remain mindful in a noisy environment). Our experts and graduate students in education and clinical psychology will provide teachers with up to 1 h per week of virtual optional consultation during the intervention to discuss any arising issues related to the intervention and its implementation. Licensed psychologists from the research team will offer psychological support to any participant who reports high levels of psychological distress and orientate them to appropriate services if needed. More information about the Open Sky School can be found on the official website https://www.ecoleacielouvert.ca/ accessible to participants.
该干预旨在每周提供约 2 小时的接触自然时间，并提供基于积极心理学的基础教学和心理健康活动工具包。Open Sky School 的原理基于日益增多的关于在自然中度过时间对心理健康益处的文献[1]。接触自然包括教师带领学生到学校 1 公里范围内的最高质量绿地，该绿地可以位于校内或校外。例如，这可以是一个校园内的森林或附近的公园。每周 12 周（包括交通），班级将总共花费 2 小时（即 2 次 1 小时访问或 1 次 2 小时访问），这与最近建议每周至少 2 小时接触自然的指南一致[16]。如表 1 所示，Open Sky School 的主要组成部分是让儿童接触自然，这嵌入在各种活动（学术和心理健康部分）中，同时提供教师培训和支援。为此，我们设计了一个包含教学和心理健康活动的在线工具包。 心理健康活动基于积极心理学（正念、儿童哲学和艺术治疗），旨在改善儿童的心理健康[17]。教学活动（法语、数学和科学）与魁北克省教育厅要求的核心理学学习能力相一致。教师将被允许使用自己的教学活动（如果使用，将被要求描述其活动），但鼓励使用工具包中提供的内容，因为它们是专业设计的，并在质量评估阶段获得了积极评价。然而，由于我们的试验主要旨在减少儿童的心理健康问题，教师必须至少开展工具包中提供的 10 项心理健康活动。工具包还包括关于在户外实施心理健康活动的最佳实践视频模块（例如，如何处理负面情绪；儿童如何在嘈杂环境中保持正念）。 我们的教育领域和临床心理学专家及研究生将在干预期间每周为教师提供长达 1 小时的虚拟可选咨询，以讨论与干预及其实施相关的任何问题。研究团队中的持证心理学家将为报告有高水平心理困扰的任何参与者提供心理支持，并在需要时引导他们至合适的服务。有关 Open Sky School 的更多信息，可访问参与者可访问的官方网站 https://www.ecoleacielouvert.ca/。

Table 1 Description of components within the intervention
表 1 干预措施组成部分描述

From May to June 2022, 34 elementary school teachers (5th and 6th grade) were invited to evaluate the quality of the 30 activities from our toolkit by answering 7 items about our activities (e.g. overall my students were engaged in the activity; I would use this activity with another class in the future) using a scale ranging from 1 (strongly disagree) to 5 (strongly agreed). Teachers were also invited to provide suggestions to improve the activity using an open response format. We received 85 questionnaires from 24 teachers reporting on 27 activities (14 mental health and 13 pedagogical). Teachers’ feedback was very positive with average ratings ranging from 4.2/5 to 4.5/5. More specifically, teachers responded that they agreed that the instructions clear and that the activities were simple to prepare and to implement. They reported that the students were engaged and liked the activity. Teachers agreed that they would use the activity in the future and recommend it to a colleague. Our research team further refined activities to incorporate teacher’s feedback.
2022 年 5 月至 6 月期间，我们邀请了 34 名小学教师（五年级和六年级）通过回答关于我们活动的 7 个项目（例如：总体而言，我的学生参与了这项活动；我将来会使用这项活动与其他班级）来评估我们工具包中 30 项活动的质量，评分范围为 1（非常不同意）至 5（非常同意）。我们还邀请教师使用开放式回答格式提供改进活动的建议。我们收到了来自 24 名教师、关于 27 项活动（14 项心理健康活动，13 项教学活动）的 85 份问卷。教师的反馈非常积极，平均评分在 4.2/5 至 4.5/5 之间。具体而言，教师表示他们同意说明清晰，且活动准备和实施简单。他们报告说学生参与度高且喜欢这项活动。教师们同意他们将来会使用这项活动并向同事推荐。我们的研究团队进一步改进了活动，以纳入教师的反馈。

Control group  对照组

Six months after the inception of the trial, elementary schools (and their teachers) in the control condition will receive an unguided version of the intervention, supplemented by an online peer support group. As the children of the control group will by then be in high school with different teachers, we will provide them with a toolkit of 10 mental health activities that they can practice alone, in addition of support via video-conference, phone or email if they require help practicing the activities from a member of the research team. As in the intervention group, we will provide support by licensed psychologists to any children who report high levels of psychological distress and orient children to appropriate services if needed.
试验开始六个月后，对照组的小学（及其教师）将收到一个无指导的干预版本，并辅以一个在线同伴支持小组。届时，对照组的儿童将升入高中，遇到不同的教师，因此我们将为他们提供一套包含 10 项心理健康活动的工具包，供他们自行练习。如果他们需要从研究团队成员那里获得帮助来练习这些活动，我们还将通过视频会议、电话或电子邮件提供支持。与干预组一样，我们将为报告有高水平心理困扰的任何儿童提供持证心理学家的支持，并在必要时引导他们使用适当的服务。

Measures  测量

Table 2 summarizes when and to whom each measure will be administered. Questionnaires will be administered before and after the intervention on campus in online format by trained research assistants or the classroom teacher. At follow-up, children will complete questionnaires online at home. We estimate that teachers will take 90 to 120 min to complete questionnaires (depending on the number of students in their classroom) and that students will take between 20 and 30 min to respond.
表 2 总结了各项措施的实施时间和对象。问卷将在干预前后在校园内以在线形式由受过培训的研究助理或班主任进行施测。在随访阶段，儿童将在家中在线完成问卷。我们估计教师完成问卷需要 90 至 120 分钟（取决于其班级学生人数），而学生回答问卷需要 20 至 30 分钟。

Table 2 Summary of measurements by informant and time points
表 2 按信息提供者和时间点的测量总结

Primary outcome: Mental health symptoms
主要结果：心理健康症状

The Social Behavior Questionnaire [18] is a 30 item questionnaire that will be used to assess a range of mental health symptoms in children. The instrument incorporates items adapted from the Child Behavior Checklist [19], the Ontario Child Health Study Scales [20] and the Preschool Behavior Questionnaire [21] used in the Quebec Longitudinal Study of Children Development [22]. The frequency of children’s symptoms over the last 2 months is rated on a scale 3-point (never/not true = 0, sometimes/somewhat true = 1, often/very true = 2). Overall symptoms will be examined as outcomes, as well as internalizing symptoms (emotional distress and withdrawal; 11 items), externalizing symptoms (impulsive/hyperactive/inattentive and disruptive behaviors; 13 items), and social behaviors (pro-social behavior and peer relationships; 6 items) [23]. See Appendix 4 for all items in the questionnaire. Ratings will be obtained by both child and teacher reports which will be analyzed separately.
社交行为问卷[18]是一个包含 30 个项目的问卷，用于评估儿童的心理健康症状。该工具整合了来自儿童行为检查表[19]、安大略儿童健康研究量表[20]以及魁北克儿童发展纵向研究[22]中使用的学前儿童行为问卷[21]的改编项目。儿童过去 2 个月的症状频率在 3 点量表上评分（从不/不真实=0，有时/有点真实=1，经常/非常真实=2）。总体症状将作为结果进行检验，以及内化症状（情绪困扰和退缩；11 个项目）、外化症状（冲动/多动/注意力不集中和破坏性行为；13 个项目）以及社交行为（亲社会行为和同伴关系；6 个项目）[23]。请参阅附录 4 获取问卷中的所有项目。评分将由儿童和教师分别报告，并将分别进行分析。

Secondary outcomes  次要结局

Additional mental health indicators for children
儿童额外心理健康指标

The Positive and Negative Affect Schedule for Child (PANAS-C) [24] is a 20-item scale that will be used to assess positive (e.g., “excited”) and negative (e.g., “upset”) affect which has good convergent and discriminate validity among children. Children will indicate to what extent they experience feelings over the last 2 weeks (1 = very slightly or not at all; 5 = extremely).
儿童积极与消极情感量表（PANAS-C）[24]是一个包含 20 个项目的量表，用于评估儿童的正性（例如，“兴奋”）和负性（例如，“沮丧”）情感，该量表在儿童中具有良好的收敛效度和区分效度。儿童将表明他们在过去两周内体验到这些感受的程度（1=非常轻微或不体验；5=极其体验）。

The Children’s Depression Inventory-Short Version (CDI-S) [25] includes 13 items that will be used to assess cognitive, affective and behavioral signs of depression in children. The CDI-S has good convergent, discriminate and factorial validity among children. Children consider how they were feeling over the last 2 weeks and respond on a 3-point scale (e.g. 1 = I hate myself; 2 = I don’t like myself; 3 = I like myself).
儿童抑郁量表-简版（CDI-S）[25] 包含 13 个项目，用于评估儿童在认知、情感和行为方面的抑郁症状。CDI-S 在儿童中具有良好的收敛效度、区分效度和因子效度。儿童需要考虑过去两周的感受，并在 3 点量表上作答（例如：1=我讨厌自己；2=我不喜欢自己；3=我喜欢自己）。

Relationship with environment for children
与儿童的环境关系

The Nature Connection Index (NCI) [26] is a self-report questionnaire including 6 items that will be used to assess connectedness to nature. The scale has good validity and reliability among children. Participants respond to affirmations (e.g. nature always makes me happy) using a 7-point scale (1 = strongly agree; 7 = strongly disagree).
自然联系指数（NCI）[26]是一个包含 6 个项目的自我报告问卷，用于评估与自然的联系。该量表在儿童中具有良好的效度和信度。参与者使用 7 点量表（1=非常同意；7=非常不同意）对肯定句（例如，大自然总是让我感到快乐）进行回答。

Pro-environmental attitude and behaviors will be measured by a brief 6-item questionnaire developed in a recent study [27], that asks children to report the frequency they made an effort to conserve water, energy and recycle trash (1 = always; 5 = never) and the extent to which they agree that they are ready to volunteer, give money and talk to their entourage to protect nature (1 = strongly agree; 4 = strongly disagree). Additionally children will be asked about their pro-environmental behaviors in the context of climate change using 4 self-report questions, adapted from a previous study and refined by experts [9, 28]. Children report the extent to which they are worried about climate change (1 = not at all worried; 4 = extremely worried), that these worries motivate them to engage in pro-environmental behaviors or activism (1 = not at all; 4 = a lot) and that they feel capable of making behavioral changes to help the environment (1 = strongly disagree; 4 = strongly agree).
环保态度和行为将通过一项最近研究中开发的简短 6 项问卷进行测量[27]，该问卷要求儿童报告他们为节约用水、能源和回收垃圾所做出的努力频率（1=总是；5=从不），以及他们同意为保护自然环境而自愿参与、捐款和与周围人谈论此事的程度（1=非常同意；4=非常不同意）。此外，儿童还将就气候变化背景下的环保行为，通过 4 个自我报告问题进行回答，这些问题改编自先前研究并由专家改进[9,28]。儿童将报告他们对气候变化的担忧程度（1=完全不担心；4=极度担忧），这些担忧是否促使他们参与环保行为或活动（1=完全不；4=很多），以及他们是否认为自己有能力通过行为改变来帮助环境（1=非常不同意；4=非常同意）。

Well-being for teachers  教师的幸福感

The World Health Organization Well-Being Index (WHO-5) [29] is a 5-item self-report measure that will assess of wellbeing for adults. The WHO-5 is a widely used, valid and reliable measure that is sensitive to change. Participants indicate the frequency of their feelings (e.g. in a good mood) over the last two weeks (5 = all the time; 0 = never).
世界卫生组织幸福感指数（WHO-5）[29]是一个包含 5 个项目的自我报告测量工具，用于评估成年人的幸福感。WHO-5 是一个广泛使用、有效且可靠的测量工具，能够敏感地反映变化。参与者需指出过去两周内他们感受某种情绪（例如心情良好）的频率（5=总是；0=从不）。

The Positive and Negative Affect Schedule (PANAS) [30] is a 20-item self-report measure that will be used to assess positive (e.g., “excited”) and negative (e.g., “upset”) affect which has well-established good psychometric properties. Teachers will indicate to what extent they experience feelings over the last two weeks (1 = very slightly or not at all; 5 = extremely).
积极与消极情感量表（PANAS）[30]是一个包含 20 个项目的自我报告测量工具，用于评估积极（例如，“兴奋”）和消极（例如，“沮丧”）情感，该量表具有良好的心理测量学特性。教师将标示出他们在过去两周内体验情感的程度（1=非常轻微或不体验；5=极其强烈）。

Appreciation of outdoor activities for children and teachers
对儿童和教师的户外活动 appreciation

An adapted version of the Enjoyment of Teaching Mathematics Scale [31] will be used for teachers from the intervention group at post-test to self-report their enjoyment of teaching outdoors (e.g. I really like teaching outdoors) with 5 items on a 5 point scale (1 = strongly agree; 5 = strongly disagree). We designed one item for children to self-report the frequency that they appreciated the intervention (1 = not at all; 4 = always) that will be administered in the intervention group at post-test.
将使用教学数学量表（Enjoyment of Teaching Mathematics Scale）[31]的改编版本，用于干预组教师在后测时自我报告他们在户外教学的乐趣（例如，“我真的很喜欢在户外教学”），该量表采用 5 点量表（1=非常同意；5=非常不同意）。我们设计了一项内容，让儿童自我报告他们欣赏干预的频率（1=完全不欣赏；4=总是欣赏），该内容将在干预组在后测时实施。

Moderator variables  调节变量

Sex  性别

The children’s sex (male, female) will be obtained via school records.
儿童性别（男，女）将通过学校记录获得。

Disability status of children
儿童残疾状况

Children formally diagnosed as having a physical or mental disability (e.g. intellectual deficiency) or having adaptation disorders (e.g. conduct disorders) or learning disorders (e.g. language deficits) will be identified via their school records.
根据学校记录，识别正式被诊断为患有身体或精神残疾（例如智力缺陷）或适应障碍（例如行为障碍）或学习障碍（例如语言缺陷）的儿童。

Green space of neighbourhoods
邻里的绿地

The Normalized Difference Vegetation Index (NDVI) will be used to quantify the density of green vegetation associated with the school’s zip code. The widely used NDVI is based on the land surface reflectance of colors which is drawn from satellite images of the earth’s surface. The index varies between + 1 and -1 with higher values indicating higher green vegetation density. We will use 2019 satellite images which are available via the Consortium CANUE [32].
将使用归一化植被指数（NDVI）来量化与学校邮政编码相关的绿色植被密度。广泛使用的 NDVI 基于从地球表面卫星图像中获取的地表颜色反射率。该指数在+1 和-1 之间变化，较高值表示较高的绿色植被密度。我们将使用 2019 年的卫星图像，这些图像可通过 CANUE 联盟获取[32]。

Deprivation indicator of the school
学校贫困指标

School’s level of deprivation will be quantified using a ranking provided by the Ministry of Education and Higher Education. The ranking is based on a composite score incorporating the proportion of students within each school whose mother completed high-school and whose both parents are employed full time. Schools are classified on a scale ranging from 1 (lowest deprivation) to 10 (highest deprivation) and scores of 8 to 10 are considered as disadvantaged [33].
学校贫困程度将使用教育部和高等教育部的排名进行量化。该排名基于一个综合分数，包括每所学校中母亲完成高中学业且父母均全职就业的学生比例。学校被分为 1（最低贫困）到 10（最高贫困）的等级，分数在 8 到 10 之间被视为处于不利地位[33]。

Experience with outdoor teaching of teachers
教师户外教学经验

Teachers’ experience with outdoor teaching over the last 3 years (e.g. context, duration) (e.g. did you practice outdoor education in autumn 2022?) and outdoor activities practiced in their leisure time will be assessed with a 6 questions that were successfully used in a previous study on school based outdoor education.
教师过去 3 年（例如，背景、持续时间）的户外教学经验（例如，您在 2022 年秋季进行过户外教育吗？）以及他们在休闲时间进行的户外活动将通过一个包含 6 个问题的评估进行评估，这些问题在之前一项关于学校户外教育的成功研究中得到应用。

Adherence assessments: Teacher Logbook
依从性评估：教师日志

The teachers will fill out an online logbook in which they will indicate information about each nature visit. They will provide information on the activities they chose to carry out (from our toolkit or others of their choice), the duration of these activities, where the activity was carried out and the total time spent outdoors. They will record if they watched our training videos, if they encountered any problems and the amount of time they spent with our supervisors. This information will be used to evaluate the adequacy of the implementation of our intervention. To fully comply with implementation, there must be of a total of 24 h of intervention (2 h per week for 12 weeks) and a minimum of 10 mental health activities from the toolkit must be carried out. Classes that do not achieve a minimum of 80% completion and comply with content 90% of the time will be excluded from sensitivity analyses. Information contained in the logbooks will be evaluated independently by two researchers and we will analyze inter-rater agreement to ensure the consistency of the codification of the information provided.
教师将填写在线日志，其中他们需要填写有关每次自然访问的信息。他们需要提供有关他们选择进行的活动（来自我们的工具包或他们自己选择的其他活动）的信息、这些活动的持续时间、活动地点以及户外总时间。他们需要记录是否观看了我们的培训视频、是否遇到了任何问题以及与我们的督导共度的时间。这些信息将用于评估我们干预措施实施的充分性。为了完全符合实施要求，干预措施的总时间必须为 24 小时（每周 2 小时，持续 12 周），并且必须至少完成工具包中的 10 项心理健康活动。未达到最低 80%完成率且 90%的时间内未遵守内容的班级将被排除在敏感性分析之外。日志中包含的信息将由两名研究人员独立评估，我们将分析评分者间一致性，以确保所提供信息的编码一致性。

Sample Size  样本量

To determine sample size for primary outcome immediately after intervention, we conducted power analyses using a Monte Carlo simulation procedure (5000 samples). On the basis of the limited literature on outdoor education [11, 12], we expect to obtain a small effect size for our primary outcome, i.e. overall mental health problems in children. With 100 classes (n≈2500) which include typically 25 students (range between 18 to 26) per class, a refusal and attrition rate of 20% (n≈2,000) pre to post-test, an inter-class correlation of 0.02, an expected effect size of Cohen’s d = 0.20 and alpha set at 0.05, we expect that sufficient power will be achieved (> 0.80) for our primary and secondary outcomes.
为了确定干预后主要结局的样本量，我们使用蒙特卡洛模拟程序（5000 个样本）进行了功效分析。基于户外教育有限的研究文献[11, 12]，我们预计主要结局（即儿童整体心理健康问题）会产生较小效应量。在 100 个班级（n≈2500）中，每个班级通常包含 25 名学生（人数范围在 18 至 26 人之间），干预前后测试的拒绝和失访率为 20%（n≈2000），班级间相关系数为 0.02，预期效应量为 Cohen's d = 0.20，α设定为 0.05，我们预计主要和次要结局的功效将足够（>0.80）。

Randomization  随机化

Randomization will occur after baseline assessments. Once randomization has occurred, it is not possible to blind researchers and participants within our design. A simple computer algorithm will be used to randomly allocate schools to two parallel and balanced conditions (intervention or control; 1:1) by an independent researcher not involved in the study. This will ensure that all schools have an equal opportunity to be allocated into one of the two groups. In the event that multiple teachers from the same school consent to participate, they therefore be allocated to the same experimental condition to avoid contamination effects. All research assistants or classroom teachers administering questionnaires will complete training sessions prior to assessment to maintain consistency and when possible, the same investigator or classroom teacher will be used at baseline and at the immediate post-intervention assessments. The evaluation at 3 months follow-up will be completed by children online at home.
随机化将在基线评估之后进行。一旦随机化完成，在我们的设计中就不可能使研究人员和参与者保持盲态。将使用一个简单的计算机算法，由一名未参与该研究的独立研究人员将学校随机分配到两个平行且平衡的条件（干预或对照；1:1）中。这将确保所有学校都有同等的机会被分配到两个组中的任何一个。如果同一学校的多名教师同意参加，那么他们将被分配到相同的实验条件，以避免污染效应。所有负责发放问卷的研究助理或教室教师，在评估前都将完成培训课程，以保持一致性，并在可能的情况下，在基线和立即的干预后评估中使用相同的研究人员或教室教师。3 个月的随访评估将由儿童在家在线完成。

Statistical analyses  统计分析

All analyzes will be done at the cluster, i.e., school, level. Dependent variables will be measured on a continuous scale. A longitudinal ANCOVA, as described in Liu et al. (2009), will be used to estimate the main effects and the moderating effects previously mentioned. Participant characteristics from the intervention and control groups will be compared at the school level, where means (e.g., school deprivation indicator) could be added to the model as covariates in the unlikely event that randomization has not unable to balance the two groups. Multiple imputation and intent to treat analyses will be used to handle missing data.
所有分析将在聚类层面，即学校层面进行。因变量将使用连续尺度进行测量。将采用 Liu 等人（2009 年）所述的纵向协方差分析（ANCOVA）来估计之前提到的主效应和调节效应。干预组和对照组的参与者特征将在学校层面进行比较，在随机分配未能平衡两组的不太可能的情况下，可以将均值（例如，学校剥夺指标）作为协变量添加到模型中。将使用多重插补和意向治疗分析来处理缺失数据。

Recruitment strategy and timeline
招募策略和时间表

For the randomized controlled trial, eligible schools will receive an initial invitation letter by email, with a 90 s video (December 2022), which they will be asked to distribute to their 5-6^th grade teachers. In the invitation letter, 5-6^th grade teachers will be invited to attend an online information session describing their expected involvement in the Open Sky School project. All interested teachers will be sent an information and consent form. Once teachers will have consented to take part in the study, they will then distribute information and consent forms to students and their parents. Parents will be invited to an online information session describing the intervention. Baseline assessment will take place from March 6^th to 10^th 2023 and post-test assessments will be conducted from June 5^th to 12^th 2023. The weekly 2 h nature visits will take place from March 13^th 2023 to June 2^th 2023. The follow-up assessments will be administered from September 18^th to 23^rd 2023. To encourage participation throughout the study, teachers will be compensated 100$CA for evaluating mental health symptoms of their students before and after the intervention (up to 200$CA total). Children can choose to be entered into a lottery to win gift cards to a local bookstore. More specifically, we will draw two 50$CA gift cards per class for children who complete questionnaires at pre and post-test, and ten 100$CA gift cards for children who the complete follow assessment. Figure 1 shows a flow chart of the inclusion of participants.
对于随机对照试验，符合条件的学校将通过电子邮件收到一封初始邀请信，附带一个 90 秒的视频（2022 年 12 月），要求他们分发给 5-6 年级的 5-6 名教师。在邀请信中，将邀请 5-6 年级的 5-1 名教师参加一个在线信息会议，介绍他们参与 Open Sky School 项目的预期参与情况。所有感兴趣的教师将收到一份信息和同意书。一旦教师同意参与研究，他们就会将信息和同意书分发给学生和家长。家长将被邀请参加一个在线信息会议，介绍干预措施。基线评估将于 2023 年 3 月 6 日-10 日进行，后测评估将于 2023 年 6 月 5 日-12 日进行。每周 2 小时的户外访问将于 2023 年 3 月 13 日-6 月 2 日进行。随访评估将于 2023 年 9 月 18 日-23 日进行。 为了鼓励在整个研究期间参与，教师将获得 100 加元报酬，用于在干预前后评估其学生的心理健康症状（最高可达 200 加元）。儿童可以选择参加抽奖，赢取当地书店的礼品卡。更具体地说，我们将为完成前测和后测问卷的每班儿童抽取两张 50 加元礼品卡，并为完成后续评估的儿童抽取十张 100 加元礼品卡。图 1 显示了参与者纳入的流程图。

Fig. 1  图 1

Flow chart of inclusion of participants Note. ^a 280 schools in 29 school boards were initially eligible. 4 school boards encompassing 32 schools did not agree to participate and were therefore removed from the recruitment process. ^b If more than 100 teachers consent to participate, we will randomly select 100 teachers to participate in the trial. ^c Parents and students must provide informed consent for students to participate in the assessments. Students who do not participate in assessments will still participate in the Open Sky School program. ^d In the event that multiple teachers from the same school consent to participate, they will be allocated to the same experimental condition to avoid contamination effects
参与者纳入流程图 注释。 ^a 最初，29 个学区中的 280 所学校具有资格。4 个学区包含 32 所学校，因不同意参与而被从招募流程中移除。 ^b 如果超过 100 名教师同意参与，我们将随机选择 100 名教师参与试验。 ^c 家长和学生必须为学生参与评估提供知情同意。不参与评估的学生仍将参与 Open Sky School 项目。 ^d 如果同一学校的多名教师同意参与，他们将分配到相同的实验条件，以避免污染效应。

Data collection, analysis and dissemination
数据收集、分析和传播

Data will be collected online using Qualtrics, a widely used software in analytics and research. Confidential data (name, zip code) will be uploaded to a private and secure computer and then periodically erased from the server. The data file that will be analyzed will only contain the anonymous (numeric) identifier and the answers to the questionnaires. The file linking the identifiers to the data file will be kept on an encrypted USB key, protected by a password and kept in a locked safe. The safe will be kept in Dr. Geoffroy's and research coordinator work office. Only Dr. Geoffroy and the coordinator will have access to it. When data collection is complete, the data will be downloaded to a private computer and then deleted from Qualtrics. Members of the research team responsible for analyzing data will only have access to this anonymous data set which will be used solely for the purpose of establishing and disseminating research findings. Results will be disseminated to researchers, stake-holders, policy-makers and participants via scientific publications, oral presentations, interviews, and vulgarizations. All communications related to the project will be made available publically on the official website https://www.ecoleacielouvert.ca/.
将使用 Qualtrics（一种在分析和研究中广泛使用的软件）在线收集数据。机密数据（姓名、邮政编码）将上传到一台私密且安全的计算机，然后定期从服务器中删除。将要分析的数据文件将仅包含匿名（数字）标识符和问卷答案。将标识符与数据文件关联的文件将保存在一个加密的 USB 密钥上，该密钥受密码保护并保存在一个上锁的保险箱中。保险箱将存放在 Dr. Geoffroy 和研究协调员的工作办公室。只有 Dr. Geoffroy 和协调员才能访问它。当数据收集完成后，数据将下载到一台私密计算机，然后从 Qualtrics 中删除。负责分析数据的研究团队成员将只能访问这个匿名数据集，该数据集将仅用于建立和传播研究成果。结果将通过科学出版物、口头报告、访谈和科普活动传播给研究人员、利益相关者、政策制定者和参与者。 项目相关的所有沟通都将通过官方网站 https://www.ecoleacielouvert.ca/ 公开。

Discussion  讨论

Potential implications  潜在影响

This study will quantify the extent to which an educational approach involving contact with nature, which is gaining popularity in the educational community, reduces mental health problems among children, while identifying the context in which the intervention is more effective. The intervention has a high potential for uptake by schools considering its flexibility and engaging activities. If successful, the program will be scaled up and used to issue guidelines for promoting mental health and healthy lifestyles in schools.
本研究将量化一种涉及接触自然的教育方法（该方法在教育界日益流行）在减少儿童心理健康问题方面的程度，同时确定干预措施更有效的环境。鉴于其灵活性和吸引人的活动，该干预措施具有被学校采用的较高潜力。如果成功，该计划将扩大规模，并用于发布促进学校心理健康和健康生活方式的指南。