Michael R. Bloomberg: School reopenings are Biden’s first big test

America’s schoolchildren and teachers have just gotten some very good news from the Centers for Disease Control and Prevention. After reviewing data from multiple studies in the U.S. and abroad, the agency has concluded that in-person schooling poses very little risk of coronavirus transmission as long as basic safety precautions are followed. That should send a clear message to governors, mayors and teachers union leaders: It’s time to open the schools.