New York City's public school district, the largest in the United States, will cancel in-person classes starting Thursday.
The school closures come as the U.S. death toll from COVID-19 surpassed a record quarter-million lives lost, while state and local officials reimpose social distancing restrictions across the country.
New York City's 1.1 million public school students have followed a staggered, part-time system of classroom instruction and online learning since September.
But Mayor Bill de Blasio announced Wednesday they would revert to distanced learning after the city's virus infection rate hit 3%.
"And I want to emphasize to parents, to educators, to staff, to kids that we intend to come back and come back as quickly as possible."
New York City, once the U.S. epicentre of the pandemic, has seen a late-autumn resurgence of the virus after a summertime lull.
It now joins other large school districts like Boston and Detroit in canceling in-person learning.
41 states have reported record increases in daily COVID-19 cases this month.
The Midwest, now the epicenter of the crisis, reported almost half a million cases last week.