This paper examines the long-term consequences of tracking in middle school. Using longitudinal administrative data from a large, urban school district and regression and quasi-experimental matching methods, we find that students who had the opportunity to take advanced math earned higher math test scores, completed more rigorous high school coursework, and were more likely to attend a four-year college. These effects largely hold across student subgroups and are relatively robust to omitted confounders. We explore some mechanisms underlying the short-term effects of taking advanced math and conclude that differences in classroom composition, rather than differences in teachers, help explain these effects. We conclude by discussing the implications of these results for efforts to improve educational equity.