Researchers and policymakers often assume that teacher turnover harms student achievement, though recent studies suggest this may not be the case. Using a unique identification strategy that employs school-by-grade level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 850,000 New York City fourth- and fifth-grade student observations over 8 years. The results indicate that students in grade levels with higher turnover score lower in both English language arts (ELA) and math and that these effects are particularly strong in schools with more low-performing and Black students. Moreover, the results suggest that there is a disruptive effect of turnover beyond changing the distribution in teacher quality. (Contains 3 figures, 17 tables, and 16 notes.)