From Classrooms to Green Spaces: A Bibliometric Journey into Sustainable Education

The education sector is essential to promoting sustainable development in light of growing environmental concerns and climate change. Schools serve as hubs for academic learning as well as the development of responsible global citizens. By encouraging eco-friendly practices, green infrastructure, and sustainability-driven curricula, the Pathway to Greener Schools concept emphasizes the incorporation of environmental sustainability into educational institutions [1]. This movement supports the urgent need for education to address environmental challenges and is in line with the Sustainable Development Goals (SDGs) 4 (Quality Education) and 13 (Climate Action) of the UN [2]. Growing awareness of climate issues and the need for educational institutions to lower their carbon footprint have been the driving forces behind the push for greener schools over the past few decades [3]. Sustainable educational models are still applied unevenly across various regions and educational systems, despite tremendous advancements [4]. A thorough review of current research trends, new themes, and possible knowledge gaps in the quest for environmentally friendly school environments can be obtained through bibliometric analysis.

Communities, teachers, and students all stand to gain greatly from the transition to greener schools. In addition to lessening their negative environmental effects, green schools also offer healthier learning environments, enhance indoor air quality, lower pollution exposure, and enhance the wellbeing of their students [5]. By incorporating sustainability into their curricula, educators can promote environmental literacy and give students the tools they need to solve ecological issues [6]. Waste reduction plans, sustainable gardening, and the use of renewable energy in schools are examples of activities that promote experiential learning and inspire students to actively support sustainability. Furthermore, by lowering operating expenses and allocating funds for educational improvements, energy-efficient school buildings eventually save money [7]. Schools must set an example and impart values that will help create future leaders who are responsible as societies transition to greener economies [8].

Even though sustainability is becoming increasingly important, many schools around the world continue to function using outdated frameworks that put academic achievement ahead of environmental awareness. Adoption of greener school initiatives is hampered by a lack of infrastructure, funding, and enforcement of policies [9]. Additionally, many educational systems limit students' exposure to practical sustainability practices by emphasizing theoretical knowledge over experiential environmental education [10]. Concerns concerning teachers' readiness are heightened by the fact that many of them lack the training required to successfully integrate sustainability into their lessons. Furthermore, unequal access to green learning environments has resulted from differences in the resources available to urban and rural schools [11]. Many developing nations find it difficult to implement eco-friendly school designs and curricula because of administrative and financial limitations, despite the fact that developed nations have made strides in this area. A thorough analysis of the literature is required to identify solutions to these issues and speed the shift to sustainable education.

Finding research trends, condensing the abundance of data on sustainable education, and deciding on future directions all depend on a bibliometric analysis of the Pathway to Greener Schools. By analyzing academic publications, citation trends, and significant research topics, this study will offer a methodical understanding of how educational institutions around the world are managing sustainability initiatives [12]. Researchers, educators, and policymakers can use the findings to identify best practices, successful models, and areas that need more research. Furthermore, by identifying workable solutions to remove obstacles to sustainability in education, this study will help close the gap between research and implementation [13]. Bibliometric analysis of the development of green schooling will assist stakeholders in creating focused interventions that support global sustainability goals as environmental concerns grow more urgent.

3.1 Trend analysis

This bibliometric study's trend analysis sheds important light on the development, significance, and level of scholarly interest in the subject of green schools between 2015 and 2024. Following the application of the inclusion criteria, 160 publications in all were taken from the Web of Science (WoS) database (Figure 1). The analysis of the research trajectory, impact, and emerging themes in sustainable education is based on these studies. According to the citation analysis, there are 1,693 citing articles in total, with 1,636 refined after self-citations are eliminated. When self-citations are eliminated, the total number of times cited drops from 2,060 to 1,889, indicating a high level of scholarly interest in green school research. The field has moderate to strong academic influence, with an average of 12.88 citations per item. The substantial scholarly contribution of research in this field is further highlighted by the H-Index of 21, which shows that at least 21 articles have been cited at least 21 times.

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Figure 1. PRISMA flowchart

The rise in publications over time indicates that researchers are growing more interested in green schools, according to quantitative data (Figure 2). This is probably due to their growing awareness of climate change, sustainability policies, and the part education plays in raising environmental awareness. Furthermore, the trend indicates a move away from theoretical discussion and toward empirical research that looks at the real application of green initiatives in educational settings. Additionally, the growing number of citing articles indicates that the topic has gained popularity in the larger discussion about sustainability and education, according to the citation patterns. The dataset's self-citations show how scholars in this area are constantly building on earlier discoveries to gain a deeper understanding of sustainable teaching practices.

Research gaps, such as the possible underrepresentation of studies in particular regions or the dearth of interdisciplinary approaches integrating education, policy, and technology in the context of green schools, are also made clear by the trend analysis. Future sustainability-driven educational practices will be greatly impacted by this analysis's deeper examination of emerging themes, important research contributors, and developing methodologies. By methodically examining publication growth, citation impact, and research influence, this trend analysis advances our knowledge of how green school initiatives have evolved in the academic literature. Additionally, it opens the door for more focused and scientifically backed sustainability projects in the field of education.

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Figure 2. Quantity of publications and citations between 2015 and 2024

3.2 Performance analysis

The Pathway to Greener Schools bibliometric data performance analysis provides a comprehensive understanding of the academic landscape and the influence of research on green schools by identifying important contributors and highly cited works. The analysis examines the most important papers, sources, writers, institutions, and nations that have contributed to this field of study.

3.2.1 Documents

One of the most influential papers in the field is the Impact of Views to School Landscapes on Recovery from Stress and Mental Fatigue [19], which highlights the importance of green spaces in promoting student well-being and has the highest citation count (436). Kuo et al. [20] highlight the benefits of green spaces in the classroom and offer compelling evidence of a causal relationship between learning and nature experiences, with 184 citations. The impact of schoolyard greening on students' mental, physical, and social-emotional health is clarified by the 100-citation study [21]. Another notable study by Bikomeye et al. [22] looks at how schoolyard greening can enhance children's physical activity and socio-emotional health and has 53 citations. In a similar vein, Goldman et al. [23] investigated the impact of green school certification on students' environmental literacy and sustainable practices, citing 48 sources. These highly cited works demonstrate the high level of scholarly interest in the relationship between green spaces and educational outcomes.

3.2.2 Sources

With 23 publications, "Marketing the Green School: Form, Function, and the Future" has established itself as a significant platform for discussions about sustainable education and is among the most influential sources influencing green school research. "Environmental Education Research" has influenced the discussion of ecologically friendly education with eight publications and 70 citations. "Landscape and Urban Planning" is the most cited source with 5 publications and 568 citations, indicating that interdisciplinary groups are becoming more interested in integrating green spaces into educational facilities. "Frontiers in Psychology" (284 citations) and "International Journal of Environmental Research and Public Health" (61 citations) further emphasize the psychological and public health components of green school initiatives. The wide range of publication sources demonstrates the interdisciplinary nature of this field, which includes education, psychology, environmental science, and urban planning.

3.2.3 Authors

One of the leading authors in the field, Stevenson, K. T., has contributed significantly to the study of green education with four publications and fifty citations. Hovinga, D. and Maas, J. have made significant progress in the environmental and health aspects of school sustainability with three papers and 61 citations between them. Additionally, Azizinezhad, R., Jozi, S. A., Lahijanian, A., and Meiboudi, H. demonstrate that there is growing interest in sustainable school environments globally with three papers and 41 citations each. The impact of these researchers' citations highlights the significance of studies with a sustainability focus in shaping educational policies and infrastructure.

3.2.4 Organizations

With 6 publications and 676 citations, the University of Illinois is ranked first among the most influential universities, indicating its substantial scholarly influence on sustainability research. Vrije University Amsterdam contributes significantly to the European discussion on green schools with five publications and 166 citations. The University of Minnesota has contributed significantly to the development of school sustainability research, with 5 publications and 254 citations. The University of Melbourne (5 documents, 44 citations) and North Carolina State University (3 documents, 30 citations) further emphasize the research's global reach, which includes North America, Europe, and Australia. These groups have taken the lead in promoting evidence-based practices, policy-driven studies, and empirical research in the context of implementing green schools.

3.2.5 Countries

The USA leads the field of green school research with 60 publications and 1,088 citations, showcasing its leadership in sustainability education policies, urban greening, and environmental literacy programs. Indonesia is a prominent contributor to the Global South, with 15 publications and 54 citations, indicating the growing interest in sustainable education in developing nations. As demonstrated by Italy (7 publications, 43 citations) and the Netherlands (9 publications, 213 citations), Europe is actively engaged in sustainable school research. China and Australia illustrate the growing significance of sustainability in Asian and Oceanic educational systems with six documents each. Additionally, Malaysia (5 documents, 27 citations) and India (5 documents, 114 citations) show how important green school initiatives are becoming in South and Southeast Asia in accordance with international sustainability goals.

3.3 Co-citation analysis

Education, psychology, urban planning, and environmental science are strongly represented in the co-citation analysis of the most cited papers in the Pathway to Greener Schools research domain. The Pathway to Greener Schools research domain's top ten most co-cited articles (Table 2) demonstrate the depth and scope of academic research on green schoolyards, their advantages, and their effects on students' cognitive, physical, and mental health. The increasing agreement among academics that incorporating natural elements into school infrastructure is crucial for holistic student development is reflected in the frequent co-citation of these studies.

Table 2. Co-citations (Top 10 articles)

The psychological and emotional advantages of green schoolyards are among the primary topics of the most frequently cited articles. Green spaces in schools have been shown to enhance mental resilience, reduce stress, and promote general well-being in a number of studies, including those by Chawla et al. [24] and Kaplan [29]. These results support the idea that natural school environments are essential for promoting emotional control and mental clarity, especially in light of the rise in student anxiety and academic pressure.

The encouragement of social interaction and physical activity is another common theme in green schoolyards. Green playgrounds promote movement and interactive play, which lowers sedentary behavior and promotes positive social interactions among students, according to studies like Bell and Dyment [25] and Raney et al. [28]. Given these findings, legislators and urban planners ought to take into account the direct influence that schoolyard design has on kids' lifestyle decisions.

Furthermore, the academic advantages of green school environments are highlighted by co-cited research. It has been demonstrated that being in nature improves cognitive function, focus, and academic performance [20, 31]. The argument for incorporating outdoor learning and biophilic design principles into educational settings is further supported by the Attention Restoration Theory (ART), which holds that natural settings aid in restoring cognitive function, lowering fatigue, and enhancing focus.

Discussions of accessibility to green schoolyards and environmental justice are also common. Low-income schools typically lack access to quality green spaces, which exacerbates health and education disparities [30]. This theme emphasizes the need for policy-driven interventions to ensure equitable access to sustainable learning environments, especially in urban and underprivileged communities.

3.3.1 Co-citation analysis by clusters

The co-citation analysis reveals four primary research clusters on Pathway to Greener Schools (Figure 3), each of which represents a distinct thematic focus (Table 3). The psychological and social well-being cluster highlights the emotional benefits of green spaces, whereas the cognitive and academic benefits cluster highlights the positive effects of nature on student learning. While the sustainability and environmental education cluster emphasizes the importance of integrating green principles into school curricula, the school infrastructure and design cluster emphasizes green architecture as a critical component of sustainable education.

The social, emotional, and psychological benefits of green school environments are the main focus of the 20 articles in this cluster. Studies such as those conducted by Chawla et al. [24] and van Dijk-Wesselius et al. [21] have shown that green schoolyards help kids develop resilience and emotional control while also lowering stress. Similarly, Dyment and Bell [27] and Raney et al. [28] highlight how nature-based learning environments encourage students to be physically active and build positive social relationships. The idea that green schoolyards foster social inclusion and equity is a key theme in this cluster [30], which shows that green schoolyard access in low-income neighborhoods. Existing studies support policy-driven strategies to ensure that all students, regardless of their socioeconomic background, benefit from school environments that incorporate nature, further support this argument [32]. This cluster positions green schoolyards as more than just aesthetic improvements by highlighting their significance for resilience-building, mental health, and equitable education.

This cluster, which consists of 15 articles, focuses on the educational benefits of green spaces in schools. Research such as Kuo et al. [20], Dadvand et al. [31] and Kuo et al. [33] demonstrate how green spaces improve students' cognitive development, focus, and academic performance. These studies provide empirical support for integrating green spaces into educational settings to enhance learning outcomes. Li and Sullivan [19] provide additional evidence for this claim by demonstrating how classroom natural views aid in stress relief and enhance cognitive function. Kaplan [29] provided a theoretical basis for these findings through the Attention Restoration Theory (ART), which explains how being in nature helps students recover from mental exhaustion and enhance focus. By showing a strong relationship between green spaces and cognitive abilities, this cluster offers convincing evidence for the design of schools with natural landscapes in order to improve educational performance.

The third cluster (12 articles) focuses on integrating sustainability into school policies and curricula. It includes studies by Henderson and Tilbury [34] and Otto and Pensini [35] on environmental education and whole-school sustainability initiatives. According to these studies, green schools not only improve their physical facilities but also help employees and students develop an awareness of the environment. Another important addition to this cluster is made by Olsson et al. [36], who examined how green schools encourage students to change their behavior and develop a greater awareness of sustainability. Malone and Tranter [37] claimed that outdoor learning initiatives in green schools enhance students' experiential sustainability education and environmental literacy. This cluster highlights the critical role that education plays in advancing sustainability initiatives, arguing that curricula, school policies, and teacher preparation programs should all incorporate green school initiatives for maximum impact.

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Figure 3. Co-citation analysis (VOSviewer visualization)

This cluster, which consists of ten articles, focuses on how school infrastructure and architecture promote sustainability and student welfare. Bell and Dyment [25] and Schneider [38] investigated how well-designed school buildings and green spaces improve students' health and academic performance. Another significant study in this cluster discusses high-performance green schools as energy-efficient, environmentally sustainable learning environments [39]. Baker and Bernstein [40] supported this claim by highlighting the importance of sustainable materials, lighting, and air quality in school construction and by connecting the caliber of school buildings to the health of their students. Additionally, Edwards [41] highlighted the impact of environmental design on learning outcomes and student engagement, reinforcing the idea that school architecture must align with sustainability goals to create conducive learning environments. In order to encourage a policy shift toward sustainable school infrastructure, this cluster recommends that green building designs be prioritized in future school developments.

Table 3. Co-citation cluster on green schools

Cluster No. & Colour	Cluster Labels	No. of Articles	Representative Publications
Cluster 1 (Red)	Psychological and Social Well-being in Green Schools	20	[21, 22, 24, 27, 28, 30, 32, 42]
Cluster 2 (Green)	Cognitive and Academic Benefits of Green School Environments	15	[19, 20, 26, 29, 31, 33, 43]
Cluster 3 (Blue)	Sustainability and Environmental Education	12	[34-37, 44]
Cluster 4 (Yellow)	Green School Infrastructure and Design	10	[25, 38-41, 45]

3.4 Co-occurrence analysis

The Pathway to Greener Schools study's main themes and possible future research directions are insightfully summarized by the co-occurrence analysis of keywords. The most common term in the field (Table 4), "Green Schools" (25 occurrences, 42 link strength), emphasizes the importance of sustainable school environments and demonstrates the broad scholarly interest in this topic. "Green Schoolyards" (12 occurrences, 54 link strength) and "Design" (12 occurrences, 56 link strength) are closely related terms that further highlight the emphasis on the physical and structural elements of sustainability in educational institutions. These terms imply that the implementation of environmentally friendly infrastructures and their impact on students and learning outcomes are the subject of a substantial amount of research.

The high frequency of child-centered terms – "Children" (24 occurrences, 108 link strength) is the keyword with the strongest link – is another noteworthy finding that supports the idea that students are the main beneficiaries of research on green schools. Growing interest in the psychological and physiological advantages of natural school environments, particularly in stress reduction and general well-being, is reflected in the prominence of "Health" (20 occurrences, 69 link strength) and "Stress" (9 occurrences, 59 link strength). The idea that green school environments promote movement, outdoor play, and social interactions – all of which are essential for both physical health and cognitive engagement – is further supported by the co-occurrence of "Physical Activity" (11 occurrences, 55 link strength).

Table 4. The 15 most frequent keywords in the co-occurrence analysis

Rank	Keyword	Occurrences	Total Link Strength
1	Green schools	25	42
2	Children	24	108
3	Health	20	69
4	Education	18	56
5	Impact	15	76
6	Sustainability	15	35
7	Green school	14	27
8	Design	12	56
9	Green schoolyards	12	54
10	Performance	12	30
11	Physical-activity	11	55
12	Stress	9	59
13	Play	9	46
14	Environmental education	9	29
15	Attitudes	9	24

The notable prevalence of "Education" (18 occurrences, 56 link strength) and "Environmental Education" (9 occurrences, 29 link strength) indicates that education is still a key pillar in this field. This demonstrates that school sustainability encompasses more than just the physical environment; it also involves curriculum development and pedagogy, with an emphasis on how green schools incorporate environmental education and encourage students to have pro-environmental attitudes. As demonstrated by the fact that "Attitudes" (9 occurrences, 24 link strength) appears as a recurring keyword, research on behavioral change and perception is an essential component of studies on sustainability education, especially when examining the long-term effects of exposure to green school environments on students' commitment to ecological responsibility.

The high frequency of "Impact" (15 occurrences, 76 link strength) and "Performance" (12 occurrences, 30 link strength) indicates that the influence of green schools is another important area of focus. These keywords show that scholars are actively examining the effectiveness of green school programs, especially in relation to the objectives of academic achievement, student engagement, environmental sustainability, and institutional efficiency. The notion that green school research is linked to more general international conversations on climate action, sustainable development, and policy-driven educational reforms is further supported by the term "Sustainability" (15 occurrences, 35 link strength).

3.4.1 Co-occurrence analysis by clusters

The co-occurrence analysis of 752 keywords (with a threshold of 52 and a minimum occurrence of 4) reveals six distinct clusters that define the Pathway to Greener Schools research landscape (Figure 4). These clusters highlight significant themes and connections in the literature with the aid of keyword frequency and link strength data (Table 5), providing a comprehensive understanding of the ways in which sustainability and education interact in green school research.

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Figure 4. Co-occurrence analysis (VOSviewer visualization)

Table 5. Co-occurrence analysis of keywords on green schools

The core concepts of sustainability in education are represented by the 15 keywords in the largest cluster, Sustainability and Environmental Education. Frequently occurring terms such as "Green schools" (25 occurrences, 42 link strength), "Sustainability" (15 occurrences, 35 link strength), and "Environmental education" (9 occurrences, 29 link strength) indicate a strong emphasis on integrating sustainability principles into school environments and curricula. The inclusion of "Attitude" and "Knowledge" suggests that research in this cluster regularly examines the ways in which green school initiatives impact students' attitudes, behaviors, and ecological awareness. Another important area of research is the pedagogical role of green schools, with studies looking at how environmental education aids in the development of a long-term sustainability consciousness in both teachers and students.

With 13 keywords, the second cluster, Health, Impact, and School Performance, looks at how green school initiatives impact students' performance and health. The fact that "Children" (24 occurrences, 108 link strength) is the most highly linked keyword in this field indicates that research in this area primarily focuses on student well-being as the primary outcome of green school designs. Research regularly evaluates how well green schools improve students' academic performance and general health, according to other widely used terms like "Health" (20 occurrences, 69 link strength), "Impact" (15 occurrences, 76 link strength), and "Performance" (12 occurrences, 30 link strength). "Design," "Framework," and "Rating system" are added to demonstrate that sustainability in education encompasses more than just theoretical frameworks; it also includes the use of practical assessment tools to evaluate sustainable school structures.

"Cognitive and Psychological Benefits of Green School Environments," the third cluster, focuses on how students' psychological and cognitive well-being is enhanced by being in natural school environments. The nine keywords in this cluster include frequently occurring terms such as "Green schoolyards" (12 occurrences, 54 link strength), "Exposure," "Attention," and "Benefits." The Attention Restoration Theory (ART), which maintains that natural environments enhance mental fatigue and cognitive function, is supported by all of these terms. The addition of "Views" supports research demonstrating that even passive exposure to greenery, such as gazing out a classroom window at trees, can enhance concentration and learning outcomes.

The fourth cluster – Green Spaces, Stress Reduction, and Health Equity – has seven keywords and emphasizes the advantages of green school environments for mental health and social equity. The prevalence of terms like "Stress" (9 occurrences, 59 link strength), "Green space," and "Environment" suggests that this field of study focuses on how nature-integrated school environments support stress reduction and emotional well-being. The term "health equity" is used to highlight research that examines variations in school access to green spaces, particularly in urban areas where environmental inequalities are more obvious. Additionally, the word "Urban" suggests that scholars are investigating the challenges and policy gaps related to creating green school environments in densely populated urban areas.

The fifth cluster, Play, Outdoor Learning, and Teacher Perspectives, is composed of six keywords that highlight the value of outdoor learning, movement, and teacher involvement in green school initiatives. The presence of "Physical-activity" (11 occurrences, 55 link strength), "Play" (9 occurrences, 46 link strength), and "Grounds" indicates that this field of study examines how schoolyard greening promotes social interaction and active learning through unstructured outdoor play. Additionally, the inclusion of "Teachers" in this cluster emphasizes the vital role that educators play in enabling experiential environmental learning opportunities and integrating sustainability into the curriculum. "Childhood" highlights the long-term effects of early outdoor education exposure on students' ecological behaviors and environmental consciousness.

The Pathway to Greener Schools' bibliometric analysis offers a thorough summary of thematic advancements, research trends, and knowledge gaps in the area of sustainable learning environments. This study methodically investigates how green schools may support academic achievement, student well-being, environmental awareness, and institutional sustainability initiatives using bibliometric techniques like trend analysis, performance analysis, co-citation analysis, and co-occurrence keyword mapping. By identifying six main research clusters, the findings demonstrate the interdisciplinary nature of green school research, which crosses the fields of education, psychology, environmental science, health, and urban planning.

One of the analysis's main conclusions is that green school environments are crucial parts of an all-encompassing educational experience rather than merely being architectural upgrades. Exposure to nature in educational settings appears to improve cognitive function (Attention Restoration Theory), potentially lowering stress levels and encouraging environmental consciousness (Biophilia Hypothesis). Additionally, studies have connected biophilic learning environments and green schoolyards to enhanced emotional resilience, increased student engagement, and better academic performance. Nevertheless, a number of obstacles still exist in spite of the expanding corpus of research, such as unequal access to green school environments, budgetary limitations, and policy gaps. Stronger educational and governmental initiatives are required to address the institutional, financial, and policy barriers that the co-occurrence analysis identifies as the primary impediments to the widespread adoption of green schools.

The findings of this study are consistent with the Sustainable Development Goals (SDGs) of the UN, specifically SDG 11 (Sustainable Cities and Communities) and SDG 4 (Quality Education). This analysis suggests that by creating more engaging, healthy, and cognitively stimulating environments, green schools enhance learning outcomes. A crucial element of SDG 4 is inclusive, equitable, and high-quality education. The findings demonstrate how incorporating green school models into urban planning can improve environmental sustainability and guarantee that all students, irrespective of socioeconomic status, have access to natural learning environments. The significance of creating sustainable urban environments is emphasized in Sustainable Development Goal 11.

To ensure that evidence-based sustainable education models are widely adopted in the future, policymakers, educators, and researchers must collaborate to close the gap between research and practice. Future studies should concentrate on addressing accessibility inequalities, creating consistent sustainability standards for educational establishments, and incorporating digital technology into green school programs. To optimize the advantages of green schools, stakeholders can create more efficient funding sources, rules, and teacher training initiatives by implementing the empirical results of this bibliometric study. Ultimately, this study supports the idea that creating healthy, involved, and environmentally conscious future generations requires sustainable school environments rather than merely being a luxury.