The country's largest public school district will begin reopening in phases for in-person learning on December 7, de Blasio said in a news conference.
The city closed public school buildings on November 19 after the city's seven-day average reached a 3% positive testing rate, the threshold set by the mayor for closing schools. All students transitioned to remote learning.
Schools will no longer be required to close when the city reaches the 3% test-positivity rate, De Blasio said Sunday.
Students will be randomly tested every week and parents will be required to sign a consent form for every student that will take in-person classes, he added.
"It's less concern about the spread when it comes to younger kids," de Blasio said. "Also the demands that our parents are going through. I feel for all our parents who are experiencing so many challenges right now, how important it is for them to have their younger kids in school, how important it is at that age both educationally, socially, but also in terms of how parents juggle all the challenges in their life."
New York Gov. Andrew Cuomo said in a press call Sunday that safely opening schools during the pandemic is "the right direction and the right decision."
Students in 3K, Pre-K and grades K-5 can resume in-person classes on December 7, said de Blasio. The city will address when middle and high schoolers can return to in-person classes in the future.
There's a "little bit of extra work to do," de Blasio said, to get District 75 schools and special education programs running. All grades in District 75 schools, which provide specialized instruction for students with significant needs, will reopen to in-person learning beginning December 10.
"Getting our kids back in school buildings is one of the single most important things we can do for their wellbeing, and it's so important that we do it right," Schools Chancellor Richard A. Carranza said in a statement.
"The unparalleled value of in-person learning for students has been evident in the first few months of school, and we will do everything we can to keep our schools safe and keep them open for the duration of this pandemic."
Nearly 330,000 students are eligible to return to school. The goal is to get as many schools as possible on a regular five-day, in-person class schedule, de Blasio said.