Schools have long played a frontline role in efforts to contain infectious diseases and prevent spread to the wider community. These include vaccination requirements, school closures during periods of high illness, and the implementation of non-pharmaceutical interventions (NPI) during outbreaks. In this paper we investigate the impact of mask mandates in schools on COVID spread. We use event study and difference-in-differences models that exploit the removal of mask mandates in districts serving 50% of public school students in the U.S. surrounding the revocation of CDC guidance recommending school masking in February and early March of 2022. We estimate that going from 0% to 100% mandated masking in a county reduces COVID deaths by 0.57 per 100k people. We further estimate that the removal of mandates during this time contributed to 21800 COVID deaths through the rest of 2022, 9% of the U.S. total that year. Due to the fact that COVID deaths among students and, to a lesser extent, school staff were rare in the U.S. given school age profiles, we argue that the bulk of these deaths were from spillovers to residents in the wider community.