2018 Yes https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193254 Sivarajah, Sivajanani North America Observational Students Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Test performance Standardized test scores from 387 Toronto schools were modeled against tree cover and species data. Tree cover, distinct from grass, predicted better academic performance. Effects were strongest in high-need schools, supporting urban forestry investment.