Using data on postsecondary outcomes of high school graduates of Chicago Public Schools, the study finds that average effects of community college attendance mask different effects for different students. Enrolling at a community college appears to penalize more-advantaged students who otherwise would have attended four-year colleges; such students represent a relatively small portion of the community college population. However, enrolling at a community college has a modest positive effect on bachelor’s degree completion for disadvantaged students who otherwise would not have attended college; these students represent the majority of community college-goers. The authors conclude that accurately describing the role that community colleges play in social stratification requires analyzing effect heterogeneity and the processes through which heterogeneity arises.