Considerable prior research would lead us to expectthat children attending schools with greener views fromthe classroom and greener schoolyards would attendmore and therefore potentially learn better. The City ofChicago offers a unique opportunity to address this possibilityat an unprecedented scale, both cross-sectionallyand longitudinally, using standardized achievementtest scores as the measure of learning.Chicago Public Schools comprises well over 400schools varying widely in their schoolyards. High-resolutionaerial photos taken in the last several years makeit possible to assess schoolyard greennessâ€”largely, theextent of grass and tree coverâ€”and use it to predictstandardized test scores. The availability of multipleyears of data and different tests in different contentareas (ISAT and ITBS scores on both reading and math)afford testing for the replicability of findings. Moreimportantly, archival information on student and schoolcharacteristics makes it possible to control for importantlikely confounds at both the student level (gender,age, grade, ethnicity, free lunch status, bilingual status)and at the school level (school size, pupil-teacher ratio,ethnic distribution, percent of students on free lunch).Finally, a schoolyard greening program conducted bythe City of Chicago in roughly 100 schools over severalyears makes it possible to look for increases in standardizedtest scores before and after school greening,again controlling for myriad other factors.This talk presents findings from a decade of standardizedtest scores, comprising roughly 1.7 millionscores for some 500,000 student-years. The results ofhierarchical linear modeling of both cross-sectionaland longitudinal data indicate that greener schoolyardsâ€”and greening schoolyardsâ€”yield higher test scores.Further, this effect seems to be heightened for disadvantagedpopulations.Currently, schools are struggling to meet federal NoChild Left Behind (NCLB) standards and thus remaineligible for federal funding. Because federal fundingconstitutes a substantial portion of most public schoolbudgets, because greening is a relatively low-cost intervention,and because the findings here involve preciselythe same achievement tests on which NCLB standardsare based, these findings may be of particular policyrelevance.