Transforming California Schoolyards from Gray to Green

Policymakers, funders, and advocates increasingly recognize the importance of trees and other vegetation in schoolyards to support the social, physical, and emotional well-being of children, and also provide rich outdoor learning environments. In California, $150 million in state  grants  from CAL FIRE have recently been allocated for the planning and implementation of schoolyard forests to support the expansion of tree canopy for cooling and other benefits. However, many public school grounds are dominated by impervious ground cover like concrete and asphalt.

Impervious surfaces contribute to the urban heat island effect, which makes schoolyards hotter and exposes students to extreme heat. This is particularly problematic in underserved communities where  tree cover  is often scarce. Transforming these asphalt-dominated schoolyards into green spaces can help create cooler, healthier, and more enriching environments for students. In cities across the US,  depaving schools  is increasingly recognized as an important step in modernizing school campuses and creating vegetated greenspaces for students. Indeed,  depaving cities  is catching on as a broader global trend. Recognizing the benefits of trees, nonprofit organizations have been advocating for schoolyard greening for several decades, and school districts have been enacting policies and programs to support landscape changes. For example, Green Schoolyards America has been  advocating  for policy changes at national, state, and district scales, and developed a  state initiative  in California to support expansion of school campus tree canopy.

This StoryMap describes the extent of impervious surfaces and other land cover classes on elementary school campuses in three California school districts, then explores the historical and contemporary policies that created and reinforced high levels of asphalt and other impervious materials, and concludes with examples of schoolyard greening transformations.

The first step in this project was analyzing the extent of different land cover types currently present on school campuses. To do this, satellite imagery from 2022 and  advanced machine learning techniques  were used. These high-resolution satellite images of school grounds provide detailed views of different surfaces, such as trees/shrubs, grass, and impervious areas (e.g. roads, blacktop, concrete, buildings). The models were trained and validated on K-5 and K-6 elementary schools in three Unified School Districts in California: Los Angeles, Oakland, and Sacramento City.

View the school boundaries highlighted in blue in the map tour below.

Land cover was categorized with an overall accuracy of 93.5%, with higher accuracy for impervious land surfaces. Impervious areas were then divided into buildings vs. non-building impervious areas, with the building data coming from  OpenStreetMap . School parking lots were manually drawn so that they could be removed from land cover calculations.

The figure above shows the percent of school land area that is impervious cover, excluding buildings and parking lots, across elementary schools in each district. Each school is represented by an individual dot in the figure. In these box and whisker plots, the thick vertical black line is the median value within a district. School grounds in Los Angeles generally have a greater amount of non-building impervious cover compared to Oakland and Sacramento. The wide spread of the data within each of the three cities shows that the amount of impervious cover varied greatly across schools within a district. Notably, Los Angeles also has around 10 times as many schools as Oakland and Sacramento. 

While there are clear benefits to schoolyard greening, the amount of impervious surfaces in schools presents a major barrier to greening projects. Historical policies and events have contributed to the expansive hard surfaces on school campuses, while current policies and other factors work to keep this pattern in place (see figure below). These policies and factors relate to land use planning in schools, funding systems that finance school construction and grounds maintenance, and administrative barriers that challenge a school districts’ ability to secure resources necessary to depave. 

Planning in California public schools has historically focused on ensuring that schools can provide enough space to house growing student populations and guarantee students consistent access to spaces for physical education. Since the 1930s, state school building seismic safety standards have compelled schools to expand outward rather than vertically and to adopt open campus designs that could accommodate additional buildings as needed, such as portables (temporary to semi-permanent structures for additional classroom space). As a result, state regulations have encouraged schools to plan their campuses with open and paved areas to accommodate new school buildings in the future. 

Moreover, between 1940 to 1965, when the majority of California’s current school building stock was constructed, asphalt was encouraged as playground surface material by school building professionals and school administrators to create durable all-weather play areas. Combined with the fact that physical education curricula have historically and continue to encourage activities that favor impervious surfaces, many playgrounds with hard surfaces endure today.

Inconsistent and insufficient school funding from the state has also prevented schools from securing resources needed to maintain schools at existing levels, let alone secure the increased resources that would be required to maintain greener campuses. Since the early 1900s, funding for school facilities construction projects have relied on local property taxes, which voters are often reluctant to approve. Simultaneously, anti-tax reforms in the 1970s have gradually decreased overall funding for school operations and maintenance. Together, these developments have likely contributed to schools prioritizing low maintenance campus designs.

Lastly, key administrative barriers challenge schools’ ability to secure resources to depave. School building regulations meant to ensure the structural safety and accessibility of schools have unintentionally resulted in onerous approvals processes for school improvement projects that involve depaving. At the same time, school districts have often found it challenging to access many of the funding opportunities that have emerged over the last 20 years to support schoolyard greening due to burdensome application processes, district objectives that may be misaligned with funding objectives, and reluctance to take on projects that involve major campus infrastructure changes.

Despite these major challenges, some California school districts have made impressive progress towards schoolyard greening and depaving, such as the examples highlighted in the Transformations section.

Read more in the UCLA policy report about depaving California schools  here .

The timeline below lists selected major state and federal policies and events that influenced the prevalence of asphalt and other impervious surfaces in California school campuses.

Normandie Avenue Elementary received a transformation through funding from the State Water Resource Control Board-funded Drought Response Outreach Program for Schools ( DROPs ) program. Through a partnership between the  Los Angeles Unified School District ,  Council for Watershed Health ,  Nature Nexus Institute ,  TreePeople , and  Studio-MLA , low-impact development best management practices were employed with the objective to achieve benefits associated with sustainable stormwater management, including the education and awareness of sustainable school landscapes. The project involved replacing 6,600 combined square feet of impermeable pavement and turf with 8,745 square feet of sustainable, climate-wise landscaping, in addition to staff training, student and community outreach, and educational materials. Read more about this project  here .

Markham Elementary’s schoolyard underwent a transformation through the Oakland Living Schoolyards initiative, a partnership between the  Oakland Unified School District ,  Trust for Public Land , and  Green Schoolyards America . The Markham project involved the transformation of a predominantly asphalt schoolyard into a more vibrant space for the students and the community. Through a participatory process and community involvement, the school’s renovation involved over 75 newly planted trees, a new soccer field, an orchard and flower garden, a jungle gym, a natural play area, and a newly painted basketball court. Read more about this project  here .

Parkway Elementary is one of Green Schoolyards America’s (GSA) schoolyard forest pilot projects. GSA staff are conducting these pilot projects with schools to test replicable approaches to provide students with access to cooler and greener schools. This ongoing project, in collaboration with the  Sacramento City Unified School District  and  Bay Tree Design , has involved school community engagement, the design and implementation of a new schoolyard forest, as well as teacher professional development. Read more about this project  here . Read more about GSA’s statewide initiative, the California Schoolyard Forest System  here .