In this article, Jessica Wolpaw Reyes investigates the link between lead exposure and student achievement in Massachusetts. Childhood exposure to even low levels of lead can adversely affect neurodevelopment, behavior, and cognitive performance. Using a panel dataset of cohorts of children born in the 1990s who were third and fourth graders in the 2000s, Reyes finds that elevated blood lead levels in early childhood adversely impact performance on later standardized tests. Accordingly, the Massachusetts state policy to reduce lead levels effectively lowered the share of children scoring unsatisfactory on standardized tests by 1-2 percentage points. Reyes shows that public health policy targeting lead has clear potential to improve academic performance and urges policy makers to give it serious consideration in this larger context.