This article examines the impacts of summer instruction and test-based grade retention in New York City. We use a research design that exploits test score cutoffs used in assignment to these treatments. We find modest positive effects of summer instruction on English language arts (ELA) achievement for students assigned to summer instruction because of poor ELA performance but find little evidence of positive effects of summer instruction on math outcomes. After netting out estimates of differential test score growth within grades across years, the estimated effects of grade retention are substantial and positive through seventh grade on both math and ELA outcomes, suggesting that the additional year of instruction in fifth grade leads to improvements in subsequent grade achievement. (Contains 4 tables, 5 figures, and 10 notes.)