The role of racial diversity at colleges has been debated for over more than a half a century with limited quasi-experimental evidence from classrooms. To fill this void, I estimate the extent that classmate racial compositions affect Hispanic and African American students at a large and oversubscribed California community college where they are minorities. I find that when minority students are exposed to a greater share of same-race classmates, they are more likely to complete the class with a pass and are more likely to enroll in a same-subject course the subsequent term. The findings are robust to first-time students with the lowest registration priority versus all students and different combinations of fixed effects (e.g., student, class, and instructor race).