Nearly 250 students in grades 7-12 will be learning from home after the cluster.
"I'm not surprised, I don't know, again, you know this is a very contagious disease," said Manhattan Borough President Gale Brewer.
School officials say 19 positive COVID cases were reported - all staff, and linked to orientation prior to school starting.
Mayor Bill de Blasio has been adamant on all school learning to be in-person this year, but there are concerns.
"If there are students whose parents are not going to take them to school, or if there's a quarantine situation, how are we going to make sure that academics are seamless and online and remote?" added Brewer.
On Saturday, a DOE spokesperson said, "We do not hesitate to intervene to stop the spread. We follow stringent guidance from health experts to prevent any further transmission by quarantining close contacts, close classrooms, and if necessary, entire buildings.
In an 'Up Close' interview with Bill Ritter, UFT President Michael Mulgrew was pressing on testing in schools.
"We're focusing on right now we need testing every week, not ever other week, especially in the elementary schools, where children can't be vaccinated, because that's our early warning system to keep those children safe," Mulgrew said.
In East Harlem, questions are swirling - are the children ready to be back at home learning?
Students will be back in the building on September 28.
MORE CORONAVIRUS COVID-19 COVERAGE
New York City COVID-19 Vaccine Tracker
New Jersey COVID-19 Vaccine Tracker
Centers for Disease Control and Prevention on coronavirus
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