A positive coronavirus test in a New York City school will trigger a two-week classroom shutdown under a reopening plan announced by the nation’s largest public school system.

If there is a single confirmed case, the entire classroom will self-quarantine for 14 days and receive instruction remotely under the plan released by Mayor Bill de Blasio on Thursday. If there are two confirmed cases in different classes, the entire school building will shut down while contact tracers investigate.

“We are doing everything in our power to keep kids healthy while ensuring they are getting the education they deserve,” de Blasio said. “These rigorous test and trace protocols will keep our students and staff safe as we start off this new school year.”

New York Gov. Andrew Cuomo, a Democrat like de Blasio, has said it is up to him to decide whether any of the state’s 700 school districts can open in September at all. Friday was the deadline for districts including New York City’s to submit their reopening plans to the state.

De Blasio and Schools Chancellor Richard Carranza previously announced a hybrid reopening plan for the 1.1 million-pupil system, with most students spending two or three days a week in physical classrooms and learning remotely the rest of the time. Parents can request full-time remote learning for their children if they prefer it.

De Blasio said Friday that schools won’t open at all unless the citywide rate of positive COVID-19 tests is below 3% — a lower number than the 5% rate that has been cited by experts as a sign that it’s safe to open schools and businesses. “This is a way of proving that we will do things the right way, setting a very tough bar but also one I am convinced we can achieve,” de Blasio said, noting that the city has been below 3% every day since June 10.

Face coverings and social distancing will be required under the plan, and school buildings will be cleaned throughout the day and disinfected at night. School staff will have priority access to free COVID-19 testing with expedited results, officials said. Every school will have an isolation room for students who are exhibiting symptoms of the virus.

Carranza said officials “are actively engaged with” with unions representing teachers, principals and other school staffers on implementing the plan.

But United Federation of Teachers President Michael Mulgrew said the plan’s safety measures don’t go far enough.

“We need randomized testing of school communities throughout the year and a vigorous contact tracing system that gives schools test results and a course of action with a 24-hour turnaround,” Mulgrew said in a statement. “What’s more, even if there are stronger safety standards in place, we still have grave concerns about the city’s ability to enforce them effectively in every school. Right now, this is not enough to protect students and staff. ”

Under the plan, students will stay together in pods or cohorts in order to facilitate contact tracing in the event of a positive case. De Blasio and Carranza, who joined the mayor at a briefing Friday, acknowledged that high schools and middle schools will look different from pre-coronavirus days when students who had English together typically split off into different classes for math, social studies and other subjects.

“In-person school this fall will not be the same as it was last fall,” Carranza said. “You just cannot have that kind of an environment given all of the safety requirements, the social distancing requirements, all of the things that we have to do to be preventative.”

Schools in New York City and across the state shut down in March to halt the spread of the virus. New York was the epicenter of the virus in the United States through much of the spring but has succeeded in keeping the rate of new infections in check.

Cuomo announced that 576 people were hospitalized for the virus statewide on Thursday, the lowest number since March 17. Just five deaths on Thursday were linked to COVID-19 statewide, down from nearly 800 a day in mid-April.

(AP)