Firefighters in Flanders responded to a fire alarm at Mount Olive High School on Sunday morning.
Smoke was found in a hallway and flames were active in a classroom when crews arrived.
Budd Lake Fire assisted as Flanders crews extended a hose line and quickly knocked down the fire. Officials say the fire was contained to one classroom.
The blaze damaged carpet and wall decorations, and smoke affected nearby areas. The building was ventilated and checked for extension.
No one was inside the school at the time.