NYC Schools Will Reopen with More Covid-19 Testing to Limit Closures

Ms. Hochul said Monday that she would send one million rapid at-home test kits, each containing two tests, to New York City schools, and those are set to arrive this week. In all, the city expects to have roughly six million rapid tests on hand by the time school starts.

Dr. Michael Mina, a former Harvard University epidemiologist, is a leading expert on rapid tests and has been a forceful advocate of using testing to keep classrooms open.

But Dr. Mina, who is now the chief science officer for eMed, which distributes at-home tests, said that testing children twice a week in classrooms where an infection was detected would simply not do enough to dramatically reduce transmission. Instead, he said, those who have been exposed should be tested every day.

By testing just twice, “you’re very likely to miss when someone becomes infectious and potentially becomes a superspreader,” he said. “This virus goes from zero to a hundred easily in a day or maybe two days.”

He considered what would happen if a child tests positive on Monday after having exposed his classmates that day at school. “They get exposed on Monday, test on Tuesday or Wednesday, and then they don’t test on Friday, but they could be an absolute superspreader on Friday,” Dr. Mina said.

Brad Lander, the incoming city comptroller, recently called on the mayor to make rapid tests available to all students and staff before Jan. 3, to help prevent a major outbreak. Mr. de Blasio said Tuesday his team had decided that plan was not feasible, but the city is still encouraging students and staff to try to get tested this weekend.

That could prove difficult for many families, because of the extremely long lines at many testing sites across the city as demand has surged.