A rapid response by fire units prevented Monday night's blaze at Cherrybrook Technology High School from causing more extensive damage.
While one demountable classroom was destroyed, numerous 000 calls reporting the fire at 8:42pm prevented further damage.
Within 10 minutes eight fire crews from the nearby area as well as police and ambulance units were at the scene to find that the demountable classroom was engulfed in flames.
The fire was out by 9:10pm.
Inspector Kel Mcnamara, Duty Commander North from Crows Nest Fire Brigade said the firefighters biggest concern had been the risk of the fire spreading to other classrooms.
''Our teams used a rapid attack to protect all surrounding exposures and ensure there were no other buildings involved,'' Inspector Mcnamara said.
Sergeant Gary Lawler from Eastwood Police said that while investigations were continuing, it appeared that the fire was not deliberately lit.
Cherrybrook High principal Gary Johnson was extremely happy with the emergency services response.
He told the Hills News it was too early to give a damage estimate.
See next week's Hills News for the full story.