A vast research literature documents racial bias in teachers' evaluations of students. Theory suggests bias may be larger on grading scales with vague or overly general criteria versus scales with clearly specified criteria, raising the possibility that well-designed grading policies may mitigate bias. This study offers relevant evidence through a randomized Web-based experiment with 1,549 teachers. On a vague grade-level evaluation scale, teachers rated a student writing sample lower when it was randomly signaled to have a Black author, versus a White author. However, there was no evidence of racial bias when teachers used a rubric with more clearly defined evaluation criteria. Contrary to expectation, I found no evidence that the magnitude of grading bias depends on teachers' implicit or explicit racial attitudes.