When schools fully reopened, the Delta variant drove many worries: Would crowded classrooms run up infection rates? Would outbreaks keep many schools closed? Could there be a normal academic year — the first since the pandemic began?

The news so far has been reassuring: A vast majority of the nation’s 50 million public school students have been in classrooms, full-time and mostly uninterrupted, this fall — whether students are masked or unmasked, teachers vaccinated or not. In fact, infection rates declined 35 percent nationally through the month of September, as many schools opened their doors.

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