Data from approximately 14,000 children in the Early Childhood Longitudinal Survey--Kindergarten Cohort were analyzed to examine the associations between children's immigrant status and their academic trajectories from kindergarten to 3rd grade, with particular attention to the effects of school environments. Growth curve modeling results indicated that most children of Latin American origin improved their reading and math scores faster than non-Hispanic White children, thus narrowing their initial score gap and sometimes even surpassing White children by 3rd grade. In contrast, although they maintained higher reading and math scores, children from East Asia and India showed decreasing scores over time, which tended to narrow their initial score advantage over non-Hispanic White children. School-level factors accounted partially for these differences. Particularly in terms of the academic trajectories, children of Latin American origin responded more to school-level factors than did children of Asian origin, who responded more to child and family background, with the exception of children from Vietnam, Thailand, Cambodia, and Laos, who responded more to school-level factors. Simulation results point to the importance of school resources for the academic trajectories of children of immigrants.