NEW YORK — The reopening of certain New York City schools will be delayed once again, Mayor Bill de Blasio announced just four days before in-school learning was slated to start. 

"Real concerns have been raised by my colleagues," de Blasio admitted. "They acknowledged that real progress had been made, but not enough and more needed to be done."  

Only 3K, pre-K, and District 75, special education, classrooms will open Monday as part of the new phased reopening plan, according to the mayor. 

Parents, teachers, students and advocates rallied and carried signs saying “We won’t die for the DOE” as they took to the streets to demand a safer school reopening plan from city and state leaders Thursday evening. 

The march was planned before de Blasio made the announcement about delays.

Many protesters said remote learning is the only way to safely educate kids at the moment.

“This has been a roller coaster since March. So it’s the same MO. They are disorganized, they are not creative and above all, they didn’t make this a priority,” said protester Olympia Kazi. 

The march kicked off at East 7th Street and Avenue B in the East Village before culminating with a rally at Columbus Park in Chinatown.

Elected officials sharply criticized the mayor, saying the city is keeping families in limbo.

“This is an abusive thing that’s happening right now. And how dare you say, 'Oh, they;re resilient.' So you’re gonna abuse that resilience? It just doesn’t make any sense,” said Public Advocate Jumaane Williams.

Kindergarten-through-fifth and kindergarten-through-eighth grade schools will open on September 29 and middle and high schools will reopen on October 1, the mayor said. 

Virtual classes will begin for students not returning to schools on Monday, Department of Education Chancellor Richard Carranza said. 

Staffing shortages, aggravated by blended learning program, spurred de Blasio to delay reopening and bring in another 2,500 teachers, 4,500 total, to help re-open schools, he said. 

But union leaders have estimated the DOE needs 10,000 more teachers to run its blended learning plan, which sends in-school learners to classrooms about three days a week and remote learners into virtual classrooms. 

Policy changes — such as canceling a live learning requirement for blended learning students — made it possible to move forward with less teachers, United Federation of Teachers union president Michael Mulgrew and Council of School Supervisors and Administrator Mark Cannizzaro said Thursday.

"This number is specifically what we think we need to get moving right now," Mulgrew said. "We're going to do another analysis later in the week."

This is the second time New York City parents have learned their kids will not be returning to about 1,700 public schools, initially scheduled to reopen on September 10. 

For weeks, parents, teachers and school staff have been raising concerns over classroom ventilation, missing school nurses, and COVID-19 testing protocols, among others, but de Blasio repeatedly argued the DOE had the staff and safety measures needed to reopen in early September. 

De Blasio defended delays by arguing parents would understand complications involved in providing an education to 1.1 million students amid a global pandemic.

One reporter, and public school parent, asked de Blasio if he owed parents an apology. 

"Everyone is trying, everyone is giving it their all," de Blasio said. "I think the vast majority of parents appreciate that we're trying to get an education to their kids."