Wearing masks, social distancing and frequent hand-washing have kept in-school COVID-19 transmission low, according to results of a pilot study in Missouri aimed at identifying ways to keep elementary and secondary schools open and safe during the pandemic. The study is part of a larger, ongoing collaboration involving Washington University School of Medicine in St. Louis, the Centers for Disease Control and Prevention, the Missouri Department of Health and Senior Services, the Missouri Department of Elementary and Secondary Education and other entities.