NEW YORK CITY - Every New York City public school building will have a certified nurse on campus when classes resume in September, Mayor Bill de Blasio promised Thursday. 

"To all the folks who have been raising that concern, I hear you loud and clear," de Blasio said. "We will be ready." 

New York Health + Hospitals will contract nurses to appear at an estimated 400 schools that did not have a full-time health care provider in March, before schools closed, de Blasio said. 

The mayor did not clarify how many nurses Health + Hospitals would hire and what type of contract they would recieve, but assured New Yorkers that the city's public healthcare system would be able to meet demand. 

"Health + Hospitals came to the rescue here," de Blasio explained. "We're all talking about how do we make this work." 

Some schools will have multiple medical professionals in the building provided through community partnerships that bring doctors as well as nurses onto city campuses, Chancellor Richard Carranza added. 

De Blasio made this announcement one week after the Department of Education released its blended learning plan for reopening schools amid the novel coronavirus pandemic. 

Public school principals have until Friday to decide which of several plans they will follow when classrooms reopen Sept. 10 and families will learn of that decision Monday.

The DOE plan has raised concern from teachers and parents over safety measures to protect about 736,000 students projected to return to classrooms in the fall. 

“We have an agreement on certain things that have to be in the schools," United Federation of Teachers President Michael Mulgrew said in an interview with NY1 Anchor Cheryl Wills. "But nothing’s actually there yet.”

On Wednesday, the New York State Nurses Association called for all schools in the state to delay reopening, citing Kaiser Family Foundation research that found 25 percent of school staff are already at high-risk for serious illness or death from COVID-19. 

The group said "it’s a worrisome sign…that pediatric ICU admissions have more than doubled just in the last six weeks."

Senior Health Advisor Dr. Jay Varma addressed concerns about schools reopening in COVID-19 hotspots - such as the one reported in Sunset Park Wednesday - explaining the city's low infection rates merited a system-wide reopening and a hyperlocal-level response was not feasible. 

"We have a very fluid environment," Varma said. "People are coming in from different areas."

But de Blasio grew frustrated Thursday when one reporter raised other outstanding questions yet to be addressed less than four weeks before schools are slated to reopen.

Those concerns include what will happen if teachers without reasonable accomodations decide not to return to classrooms and how special needs students would be served in a socially distanced setting. 

"We're in the middle of a pandemic," de Blasio snapped. "Things are not going to be perfect."