The purpose of this study was to investigate correlations between the greenness surrounding public elementary schools and student academic performance in both Math and English. The authors of this study note that past studies in the literature address benefits to physical and mental health from exposure to nature, however few address benefits to academic achievement. Thus, this study examined the researchers' hypothesis that the proximity to trees and vegetation (greenness) surrounding schools has a positive impact on school-based performance.
The focal geographic areas of study included the five major cities of Massachusetts, including: Boston, Worcester, Springfield, Lowell and Cambridge. This study analyzed 3rd grade Math and English scores from 905 public schools on the Massachusetts Comprehensive Assessment System (MCAS) for years 2006-2012. Researchers used the MCAS Composite Performance Index (CPI) measuring the percentage of students scoring “Above Proficient” (AP) as the school-based measurement on which to compare schools. Researchers controlled for differences between schools based on school-level data on race, family income, student-teacher ratio, attendance, gender, and English as a primary language.
The researchers calculated the distribution, type and properties of vegetation exposure within the school vicinity obtained from NASA's Earth Observing System's remote sensing techniques of satellite imagery that converts data into the Normalized Difference Vegetation Index (NDVI). Researchers obtained NDVI data each year during the the spring (March) and fall (October) of the school year, as well as in July to measure maximum greenness exposure. Also, researchers collected data for the following four zones of increasing circular distance around each school: 250-, 500-, 1,000- and 2000-meters.
In examining the relationship between greenness and test performance after adjusting for levels of urbanization, income levels and gender, researchers found spring greenness data particularly compelling; Spring is when children take the MCAS. March outcomes revealed a highly significant association between school performance in both Math and English and surrounding greenness, particularly as the buffer zone widened. Results from July and August suggest that children with higher levels of exposure to greenness during the balance of the year show better academic performance. However, researchers found that the surrounding greenness effects in October were less clear, possibly due to the “Fall effect” as deciduous trees appear less green and reflect light differently which lowers NDVI values; therefore, school areas that are actually more green will, paradoxically, look more "dead" in the fall than areas with fewer trees. The relationship between greenness and academic test performance was stronger as larger buffer zones were considered. Researchers were unable to directly assess greenness surrounding students' homes, however, because students in public schools attend the school nearest their home, home greenness was likely captured within the wider buffer zones of the school. Therefore, the wider buffer zone likely captured a more accurate picture of total exposure to greenness.
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