NEW YORK - New York City public schools will begin to reopen starting Monday, December 7, Mayor Bill de Blasio announced Sunday.

Students in 3-K, pre-K and grades K-5 will be the first to return to in-person learning, followed by children with special needs on December 10.

“We are focusing on the younger grades,” de Blasio said. “We know first of all, studies consistently show that younger kids are having less of a negative experience and there’s less concern of the spread when it comes to younger kids.”

In a big switch, the city will also move to provide five days a week of in-person instruction.

"Some schools will be able to go to five days a week right away, they're already -- some have already done it, some have been planning for it and will be able to do it right away," de Blasio said. "Some will need more time to get ready."

Only students who have already signed up for blended learning will be able to return, and the vast majority of the city's one million students have opted to learn online only. About 330,000 have chosen blended learning, and 190,000 of them attend the schools that will be re-opening in this wave. The mayor provided no timeline for re-opening middle or high schools.

“We’re going to address in the future middle school and high school but we’re not ready for those yet. We will work to get to that day but we are not there yet,” he said.

The announcement comes less than two weeks after the mayor closed schools when the city’s infection rate hit 3%. At the time, the percentage of coronavirus cases inside school buildings was much lower, according to the de Blasio administration, but the mayor said he decided to stick with the 3% threshold because that's the number he had set prior to the reopening of schools in September. 

The mayor is now adopting an entirely new approach, which will abandon the 3% threshold and increase testing of public school students. Instead of once-a-month testing, students will be tested on a weekly basis. And only students who have signed testing consent forms will be allowed to return to the classroom, the mayor said.

Children can bring the form in on their first day back in the classroom, or parents can sign in advance by visiting Mystudent.nyc.

The mayor said his new approach to schools will last through the distribution of a vaccine, adding that there will be another 'opt-in' period for blended learning once the health situation changes.

“If we do this right, we will be able to serve the families who want to be in person better. And for the families that are remote, the day will come when the health situation changes substantially, particularly with the vaccine, and then we're going to rework the equation again. That will be another time when we reset the equation and offer people new opportunities,” he said.

Schools in orange zones may require more safety measures and testing to reopen. De Blasio said he will work with the state to make sure the infection rate in those schools is low enough. Currently, Staten Island is the only borough with designated orange zones. 

Gov. Andrew Cuomo, who had urged the city to reconsider closing schools, applauded the decision to reopen them.

"I think that's the right direction," Cuomo said Sunday during a call with reporters. "We do have new facts and new information on schools, and just about every professional says the schools - especially K-8 - should be kept open whenever it's possible to keep them open safely."

The city’s seven-day rolling average is 3.9%.