Latino students are at risk for poor social and academic outcomes in American schools, yet contextual models for understanding this risk have been elusive. Considerable research has attempted to understand the relation between the ethnic composition of schools and outcomes for Latino students, with inconsistent findings. It was hypothesized that school ethnic composition would be differentially related to outcomes in this population of students, depending on other school contextual factors. Using secondary data from the National Longitudinal Study of Adolescent Health (Add Health), the present study examined individual and school-level moderators of the slopes of same-ethnicity representation (i.e., the percentage of same-ethnicity peers) and ethnic diversity predicting feelings of school belonging and the odds of high school completion among Latino youths. The results illustrate moderation of the slopes of ethnic composition variable depending on the socioeconomic status (SES) of schools as well as the extent of academic tracking. In low SES schools, same-ethnicity representation was positively related to both outcomes (belonging and completion) when academic tracking was low. In high SES schools, the slope of same-ethnicity representation predicting the odds of high school completion was negative under conditions of low ethnic diversity. Diversity was itself positively associated with high school completion across contexts, yet this relation was moderated by SES at the student level. Specifically, the association between diversity and completion diminished as student SES decreased, relative to the mean SES of students in a school. Altogether, the results suggest that conditions associated with reduced inequality among students, namely low systemic strain (higher SES) and low academic tracking, are related to more positive associations between both same-ethnicity representation and diversity, and social and academic outcomes for Latino students. Future research is advised to consider the intersection of school ethnic composition with other aspects of the school context as well as with characteristics of individual students.