The spread of Covid-19 led to social restrictions of various kinds, of which closing schools was one. This paper studies the effect of school closures on parental labor supply. To this end, I use repeated cross-sectional data on households at the monthly level from the US Current Population Survey (CPS), and employ a difference-in-differences methodology where I compare the labor market outcomes for parents to school-aged children that require supervision with parents to slightly older children, before and after March 2020. The results show that there is a significant reduction in the labor supply of parents to younger children as a result of school closures, and that the effects are larger for mothers than for fathers.