This paper explores the effects of high grading standards on student test performance in elementary school. While high standards have been advocated by policy-makers, business groups, and teacher unions, very little is known about their effects on outcomes. Most of the existing research on standards is theoretical, generally finding that standards have mixed effects on students. However, very little empirical work has to date been completed on this topic. This paper provides the first empirical evidence on the effects of grading standards, measured at the teacher level. Using an exceptionally rich set of data including every third, fourth, and fifth grader in a large school district over four years, we match students' test score gains and disciplinary problems to teacher-level grading standards. In models in which we control for student-level fixed effects, we find substantial evidence that higher grading standards benefit students, and that the magnitudes of these effects depend on the match between the student and the classroom. While dynamic selection and mean reversion complicate the estimated effects of grading standards, they tend to lead to understated effects of standards.