It was unclear if the individual at the Watching School in Montclair was a staff member or student.
Those who had close contact with the individual have been notified and instructed to quarantine, Montclair Schools Superintendent Dr. Jonathan Ponds said.
"As always, we appreciate our community’s support and cooperation," Ponds said.
"You can assist us by remaining vigilant but sensible in your approach to dealing with this global health concern."
It was not clear if students were learning in schools or online, or through a combination of both.
Click here to follow Daily Voice Parsippany-Troy Hills and receive free news updates.