Previous research on the relationship between greenness and academic achievement has focused primarily on elementary school populations. While some studies have considered high school populations only and others have studied elementary and secondary grades together, none have investigated the greenness-achievement relationship in 6th graders alone. This study addresses this gap.
This study was based on data from 450 public schools and 49,255 sixth-graders in Washington State. Schools included in the sample represented over 80% of the total number of public schools in the state serving sixth grade students. Data included two measures of greenness around schools and two measures of academic achievement of sixth grade students. Greenness data included tree canopy cover and total green cover at 250-meter and 1000-meter radial buffers around a school. Academic achievement data was based on the percentage of students meeting or exceeding state standards in reading and math. Data was also collected on 17 potential confounders, including student characteristics, school resources, size, and location. Though the analysis is correlational and cannot offer causal inferences, three causal questions framed the study: (1) Could greening boost achievement in sixth graders? (2) If the observed greenness-achievement relationship is causal, what might be planted to boost achievement most effectively? and (3) If the observed greenness-achievement relationship is causal, where might greening efforts best focus?
The results showed that “green cover surrounding schools significantly and positively predicts achievement in sixth grade students”, even after all the confounders were considered. Of the different types of greenness, tree canopy proved to be a stronger predictor of achievement than other forms of vegetation, including grass, shrubs, and agricultural land cover. Trees thus proved to be “the primary driver behind the greenness-academic achievement link”. Other forms of green cover did not seem to contribute to this link. Nearby trees had more powerful associations with achievement than did more distant tree cover.
This study found that greener schools had higher sixth grade test scores. These findings suggest that middle school students may get an academic-achievement boost from school greening, especially if greening efforts prioritize the inclusion of trees in and around school grounds. “If a community wanted to experiment with greening schools for academic achievement, these findings provide clues as to what might be best to plant and where, suggesting that planting trees within 250m might maximize any effect on achievement.” Focusing on sixth-grade students may be especially impactful, in that the transition from elementary school tends to be particularly difficult for many students. What students experience during this transition can “significantly and negatively impact academic achievement, not only in middle school but sometimes beyond.” If greening can potentially ease the transition, planting trees in and immediately around schoolyards is a good investment.
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