Fire Chief Barry Bondurant said Monday that arson was the cause of the fire, which started in a boy’s restroom.
He added that total damage was estimated at $200,000.
No one was hurt in the two-alarm fire that was apparently set shortly after classes ended for the weekend.
Officials said Monday that the fire was still under investigation.
Classes, however, resumed Monday at the school.
About 50 school employees joined a company that specializes in fire clean-up, working all weekend to ensure the building would be ready for classes, said Richie Escovedo, a spokesman with the Mansfield school district.
The boys’ restroom was still unusable Monday, but Escovedo estimated it would be open again at about mid-week.
-- Bill Miller