Closig schools has been the core of the US pandemic influenza control strategy since the second Bush administration. There were detailed simulations showing that shutting schools is the only single intervention that can significantly affect R: schools are the best place for spreading influenza due to the very small spacing between seats in classrooms, the number of students who pack into schoolbusses daily, etc. (However, the studies were done before masking everyone was a possibility.)
Most parents with k-8 children should know this first-hand. Memory is fading but as I recall, two weeks after school year started we could pretty much expect a bug to come home. (continuing through out the winter months of the school year)
