NEW YORK (CBSNewYork) -- New York City teachers returned to school Tuesday, but hundreds were instructed to stay home because their classrooms still need ventilation repairs.
Instead of welcome back signs, notices were plastered across 10 buildings letting staff know it was another work-from-home day.
"We have schools that are having ventilation issues," United Federation of Teachers President Michael Mulgrew told reporters Tuesday morning. "The schools that were not deemed safe are not opening."
"If any classroom is not ready, it will not be used. It would only be used when it's ready," the mayor said Tuesday. "But, thank God, the overwhelming majority of classrooms are ready right now."
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Schools Chancellor Richard Carranza said he expects most to be ready by the start of in-person learning on Sept. 21.
"Now that there are 10 buildings that we've identified as needing repairs across the board, we're prioritizing these buildings to get all systems up to par by the 21st of September," he said. "Meanwhile, staff at those buildings will be temporarily working from home.
"The vast majority of the work that needs to be done in those classrooms is what I would consider minor and not capital. So there are little things that need to be done, but keeping our promise we said we would make sure everyone would have functioning ventilation," Carranza added.
The UFT will monitor schools to make sure ventilation issues are resolved. The union president said officials are being as transparent as possible and made the right call.
"Once you start getting somewhere around 50% of classrooms don't have proper ventilation, you're going to deem the building not ready to open," said Mulgrew.
"We are not putting life against learning," Randi Weingarten, president of the American Federation of Teachers, added.
WATCH: Teachers Union President On School Ventilation Issues
The High School for Leadership and Public Service in Lower Manhattan was one of the schools that failed inspection.
Melissa Ramos is an English teacher there and said some of her windows don't even open, but she added she doesn't need a classroom to teach.
"I was relieved. I was waiting, because I knew that the ventilation issues were ongoing," she told CBS2's Hazel Sanchez. "Remote learning is going to be strong until we can enter the building."
However, the shutdown has some parents worried.
"It just speaks to the city not doing what they should have been all along," Simon Skinner told CBS2.
"It's a problem. They've got to get their act together," said Alex Sakin.
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De Blasio also announced Tuesday free child care will be available for 30,000 students on the days they are learning remotely.
Spaces will be set up in community centers, cultural institutions and outside areas.
"We know that working parents will need a helping hand. So Learning Bridges will provide support by offering free child care on remote learning days for families whose children are enrolled in blended learning," Deputy Commissioner for Youth Services Susan Haskell explained.
The so-called "Learning Bridges" program will prioritize families with the greatest need, and the city hopes to expand to 100,000 seats by December.
"The parents who need it most will get the first seats and then we'll build out from there," de Blasio said.
"For students in K-8, you'll have support for your remote learning activities. It will also be balanced, with physical fitness and STEM activities," Haskell added.
Students will be grouped with their classmates as much as possible to prevent the spread of COVID-19.
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