The racial interactions between teachers and students can influence student performance in several ways. For example, pupils may trust and respect someone with whom they share a salient characteristic, making learning come more easily. Likewise, a teacher of the same race may serve as a more effective role model, boosting students' confidence and enthusiasm for learning. However, while such role-model effects are widely believed to be important, there is actually little direct empirical evidence that they exist. This study, known as Project STAR (Student Teacher Achievement Ratio), makes use of data from a randomized field trial conducted in Tennessee to produce higher-quality information on this controversial subject than has been available previously. Although Project STAR was not designed to evaluate the relationship between students' performance and their assignment to teachers of their own race, the study's randomized pairings of students and teachers provided an excellent opportunity to do so. The results showed that Black students learned more from Black teachers and White students from White teachers, suggesting that the racial dynamics within classrooms may contribute to the persistent racial gap in student performance, at least in Tennessee. These results clearly support the conventional assumption that recruiting minority teachers can generate important achievement gains among minority students. However, they also suggest that a typically overlooked cost of such efforts may be a meaningful reduction in the achivement of non-minority students. (Contains 3 figures.)