An extensive theoretical and qualitative literature stresses the promise of instructional practices and content aligned with minority students' experiences. Ethnic studies courses provide an example of such "culturally relevant pedagogy" (CRP). Despite theoretical support, empirical evidence on the effectiveness of these courses is limited. We estimate the causal effects of an ethnic studies curriculum, using a "fuzzy" regression discontinuity design based on the fact that several schools assigned students with eighth-grade GPAs below a threshold to take the course. Assignment to this course increased ninth-grade attendance by 21 percentage points, GPA by 1.4 grade points, and credits earned by 23. These surprisingly large effects suggest that CRP, when implemented in a high-fidelity context, can provide effective support to at-risk students. [This paper was published in "American Educational Research Journal" v54 n1 p127-166 2017 (EJ1132535).]