Up to 450 students and staff have been evacuated from Belconnen High School on Murranji Street in Hawker after a faulty electric switchboard caused a fire at the school.
The Emergency Services Agency said staff and students had been evacuated as a precaution about 11.25am and at at 1.25pm they remained in the school gymnasium awaiting the return of power.
Three fire pumpers were sent to the school along with the hazardous material unit, the breathing apparatus van and one commander.
Firefighters put out the fire and ventilated the area and were expected to leave the school about 1.30pm.
Technicians will remain at the school during the afternoon until power is restored and repairs are completed.
An ACT Emergency Services Agency spokesman said damage to the school was minimal and there were no injuries.