Previous research shows ethnic minority students to receive different grades when taught by majority teachers. This may happen either because of bias in teachers' grading, or because objective student performance is indeed altered. Using an experiment, I examine whether teachers grade minority and majority students differently for the same work. I find no evidence for this. However, teachers report lower expectations and unfavorable attitudes that both likely affect their behavior towards minority students, potentially inducing them to perform below their ability level. Effects of having majority teachers on minority students' grades therefore seem more likely to be indirect than direct.