The school's fire alarm went off around 3:20 a.m. Sunday and the fire department started receiving phone calls about the blaze shortly afterward, Battalion Chief Tom Mulvihill said.
Firefighters arriving at the school, located at 41800 Blacow Road, saw the building in flames, Mulvihill said.
The blaze was controlled in about 20 minutes. Firefighters remained at the school until about 6:30 a.m. conducting overhaul. The fire destroyed an art classroom, caused moderate damage to a special education classroom and also damaged a third classroom, Mulvihill said.
Mulvihill estimated the damage to the building to be about $100,000 and damage to the contents of the classrooms to be about $10,000.
Investigators returned to the school today to try to determine the cause.
A message from Principal Pete Murchison on the school's Web site states the school is open today and that classes from the affected classrooms will meet in temporary locations.