But Ventilation Action Team inspectors say 21 schools housed in ten buildings throughout the city are unfit for teachers to return to, due to poor ventilation.
The Department of Education (DOE) is calling this a temporary delay for the teachers at those schools, who cannot return to their buildings as the city works to make the needed repairs.
One of the ten buildings - out of a total of 1500 school buildings in the city - is Martin Luther King on Manhattan's Upper West Side.
MLK houses multiple schools.
The teachers' union says the discovery was made during union-required inspections, and that the buildings which failed are being shut down indefinitely.
RELATED | New York City delays opening public schools amid threat of UFT strike
The DOE says it will complete repairs on the affected buildings before in-person learning starts on the 21st.
"If there's a problem, obviously there's some time to fix them," said Mayor Bill de Blasio. "But we've been really clear: if, for any reason, a classroom is not ready for the first day of school, it'll be held back. If there's a building with a problem, we either fix the problem, or we even hold that back."
City officials say if repairs are not possible, they will be looking for alternative spaces.
Meantime, teachers in the 21 schools now sidelined for repairs will begin the school year working from home.
The list of impacted schools includes:
- PS 45 - Horace E. Greene School
- PS 45 - Horace E. Greene School (Annex Building)
- The Maxine Greene HS for Imaginative Inquiry, Urban Assembly School for Media Studies, High School for Law, Advocacy and Community Justice, High School of Arts and Technology Manhattan / Hunter Science High School Special Music School
- P.S. M721 - Manhattan Occupational Training Center, Harvest Collegiate High School
- Leadership & Public Service High School
- P.S. Q222 - Fire Fighter Christopher A. Santora School
- The Riverview School, P.S. 110
- P.S. M094, Sixth Avenue Elementary School
- Success Academy Charter School - Harlem 1, Success Academy Charter School - Harlem 3, Manhattan Academy for Arts & Language, Murray Hill Academy, Unity Center for Urban Technologies
- High School of Economics and Finance
In addition to repairs, the Division of School Facilities also taking the following steps to improve air circulation:
- Installing portable High Efficiency Particulate Air (HEPA) filters in rooms.
- Flushing air two hours before and after occupation.
- Upgrading MERV-8 to MERV-13 filters where appropriate.
UFT President Michael Mulgrew released the following statement:
"Keeping everyone safe is our top priority. Inspections by the DOE and the UFT identified these serious ventilation issues, and we will continue to monitor these buildings and other schools to make sure all ventilation problems are solved. Where repairs and upgrades cannot be made, we will work with the DOE to help find alternative space before students return Sept 21."
The mayor said the good news is that 96% of all 64,550 classrooms passed inspection and that all 1,485 buildings have now been inspected.
Amid the threat of a teacher strike Mayor Bill de Blasio announced last week that the start of the school year would be delayed.
It was announced that in-person learning in New York City public schools would be pushed back until September 21 with remote learning set to begin on September 16.
School was previously scheduled to begin with a blended approach on September 10.
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