Science’s COVID-19 reporting is supported by the Heising-Simons Foundation. A careful analysis of health data from Sweden suggests keeping schools open with only minimal precautions in the spring roughly doubled teachers’ risk of being diagnosed with the pandemic coronavirus. Their partners faced a 29% higher risk of becoming infected than partners of teachers who shifted to teaching online. Parents of children in school were 17% more likely to be diagnosed with COVID-19 than those whose children were in remote learning. Whether the harms of school closures outweigh the risks of virus transmission in classrooms and hallways has been the subject of intense debate around the world. Outbreaks have demonstrated that the virus can spread via schools to the wider community at least occasionally, and some data suggest teachers have higher than average risk of infection. However, it has been difficult to separate school-based transmission from other confounding factors, especially because schools have tended to open or close in concert with other restrictions lifting or tightening.