A 2021 study by Stanford economist Thomas Dee found that traditional public institutions lost 1.1 million students in the fall of 2020, largely driven by a substantial departure of kindergarteners and elementary schoolers. The decline was 40 percent higher in districts that provided only remote instruction at the beginning of that academic year. A separate analysis from the conservative American Enterprise Institute found larger, more sustained enrollment drops between 2020 and 2022 in districts that kept schools closed longer and enforced mask mandates when students returned to campus.