Using the Early Childhood Longitudinal Study, Kindergarten Cohort, this study examines the role that bilingualism plays in children's academic developmental trajectories during their early school years, with particular attention on the school environment (N = 16,380). Growth-curve results showed that despite starting with lower math scores in kindergarten, Mixed Bilingual children fully closed the math gap with their White English Monolingual peers by fifth grade. However, because non-English-Dominant Bilinguals and non-English Monolinguals started kindergarten with significantly lower reading and math scores compared to their English Monolingual peers, by fifth grade the former groups still had significantly lower scores. School-level factors explained about one third of the reductions in the differences in children's academic performance.