Tempe police say the 15-year-old boy is accused of intentionally starting a fire inside a gym locker in the boys' physical education locker room on Thursday morning.
The name of the teen isn't being released because he's a juvenile.
Police say he's facing charges of arson of an occupied structure, aggravated criminal damage and interference with or disruption of an educational institution.
No students were in the locker room at the time.
A school employee inside the building smelled smoke, called 911 and extinguished the fire.
Police say the fire was confined to a small area and didn't spread throughout the building.