Superintendent Adam Dewberry said firefighters found a fire on level three of a dormitory area in the school.
“Firefighters searched the area to find the scene of the fire. That has been located and the fire was extinguished,” Dewberry said.
“We have got about 55 evacuated, no major injuries reported at this stage.”
Local traffic diversions are in place at Albion and MacPherson street in Waverly.
Fire and rescue crews are using thermal imaging cameras and gas detectors to ensure the area is safe.
An investigation into the cause of the blaze is underway.