The Department of Education revealed Thursday that 900 additional classrooms require lead paint remediation before the beginning of the school year.

That brings the total number of city classrooms found to contain peeling or exposed lead paint to more than 1,800, according to the DOE.

The marked increase came after the agency expanded testing to first-grade and pre-K classrooms along with other areas, officials said.

Of the 8,428 classrooms that have been inspected in recent months, a total of 1,858 needed remediation, according to the DOE.

After an initial outcry, the department also announced Thursday that it would be testing common areas — including gyms and cafeterias — for the presence of hazardous lead-related conditions.

The DOE has vowed to remediate all impacted classrooms prior to the start of classes on Sept. 5.

That process involves covering up the exposed lead-tainted area with a primer before sealing it with lead-free paint.

City principals were notified of the DOE’s lead findings and parents will be informed via emails and letters.

While parents and elected officials have expressed concerns about the presence of lead in city schools, Chancellor Richard Carranza tried to downplay it earlier this month.

“The Earth isn’t falling, the sky isn’t falling, our children are not in grave danger,” Carranza told members of the Chancellor’s Parent Advisory Council.

DOE testing came after a WNYC/Gothamist investigation found lead contamination from paint in several schools along with lead-laden dust 100 times greater than safety standards.

The DOE — which said it will conduct periodic lead monitoring during the school year — tested school buildings built before 1985.