North Brunswick High School is expected to remain closed until lab results on mold come back.
According to district officials, part of the problem is the school's air conditioning unit was down earlier in the summer.
The school is closed today because of Rosh Hashanah.
More than a dozen schools across New Jersey had to delay the start of the new school year or section portions of their buildings because of mold.
In Hopatcong, students will not be going to school until Friday because of mold.
Most have been re-mediated and will be tested again.