There is a longstanding debate over the extent to which contextual factors, particularly those derived from compositional characteristics, influence individual achievement. Using a comprehensive large urban school district longitudinal administrative data set covering student demographics, zoned vs. enrolled school data, and Stanford 10 achievement test scores for all students enrolled at any point in 2007-08 to 2011-12, we investigate the unique mechanisms by which school context affects academic performance. In specific, our study analyzes how certain racial/ethnic and socioeconomic contextual characteristics impact mean performance and achievement growth for specific groups of students along with the presence of attainment gaps between these groups. These findings will illuminate the effects of school contexts and ultimately provide a framework for urban districts to understand the types of environment most conducive to achievement across various race/ethnic and socioeconomic status groups.