I don't know anyone who reasonably disagreed with closing down for the rest of the 2019-2020 school year after March. There were essentially only 2 months left, and there was uncertainty about the best approaches. By summer, however, there was plenty of information.
Fatality Rate for COVID was essentially zero for ages 0-19. Kids fared better with COVID than they did with the flu. You didn't even get to 0.1% I.F.R. until you got to age 50-plus. Schools should have been re-opened in the fall. We knew what precautions were effective. This wasn't "hindsight 2 years later."