Authorities say P.S. 8, P.S. 10 and Hope Academy in Passaic were evacuated shortly after 10:00 a.m.
A bomb squad searched the schools, but found nothing.
P.S. 10 was cleared about a half-hour after the incident began.
The all clear was given at the other schools around 11:00 a.m.
Passaic city police and fire departments are investigating, along with the Passaic County Sheriff's Bomb Squad and Prosecutor's Office investigator.