New York schools will only reopen in September if coronavirus levels remain low and stable, Gov. Andrew Cuomo announced Monday.

While Mayor Bill de Blasio declared last week that the nation’s largest school system would come back to life in September, Cuomo warned that a spike in infections would halt that effort.

“If you have the virus under control, reopen,” he said. “If you don’t have the virus under control, then you can’t reopen.”

If the infection rate in a given region is under 5 percent for 14 days, schools in that area can unlock the doors, Cuomo said.

But if it spikes to over 9 percent over seven days, schools will be shuttered.

State officials will examine data in the first week of August to make an initial determination.

“We’re not going to use our children as a litmus test and we’re not going to put our children in a place where their health is in danger,” Cuomo said.

As of Monday, schools in all state regions would qualify for a September kickoff.

State education officials also issued reopening guidelines Monday that mirrored the scenario de Blasio presented last week.

Schools would be compelled to observe social distancing, a practice that would require staggered classes and remote instruction multiple days a week.

That prospect has caused deep unease among parents who will likely be required to find and finance daycare during the school year.

In addition, students in the city and across the state will be subject to regular temperature checks and other coronavirus-related precautions.

The state Board of Regents said Monday that all students and teachers would be required to wear masks.

Cuomo said more detailed reopening guidance would be available Wednesday and that districts would have to submit their individual proposals by the end of the month.