The goal of this study was to examine the mechanisms underlying associations between neighborhood socioeconomic advantage and children's achievement trajectories between ages 54 months and 15 years. Results of hierarchical linear growth models based on a diverse sample of 1,364 children indicate that neighborhood socioeconomic advantage was nonlinearly associated with youths' initial vocabulary and reading scores, such that the presence of educated, affluent professionals in the neighborhood had a favorable association with children's achievement among those in less advantaged neighborhoods until it leveled off at moderate levels of advantage. A similar tendency was observed for math achievement. The quality of the home and child care environments as well as school advantage partially explained these associations. The findings suggest that multiple environments need to be considered simultaneously for understanding neighborhood-achievement links. (Contains 9 footnotes, 5 tables, and 1 figure.)