Schools are indeed quite safe. The younger the safer, but generally children get sick less and are vanishingly unlikely to end up in the hospital or die. There's also evidence that schools haven't been a big transmission sites for covid probably because while teacher to teacher transmission is as big a problem as anywhere teacher <-> student and student <-> student transmission isn't that likely. The other side is that closing schools has had big negative impacts on children especially poor children.
https://www.cdc.gov/coronavirus/2019-ncov/science/science-br... https://jamanetwork.com/journals/jamanetworkopen/fullarticle...