Police have appealed for witnesses to come forward after a school was damaged during a fire at St Clair overnight.
About 1.30am today, emergency services were called to Endeavour Avenue after reports that St Clair High School was on fire.
Fire and Rescue NSW deployed more than 25 appliances to fight the blaze which appears to have seriously damaged the south western side of the school which houses science blocks, the canteen and a number of classrooms.
Fire fighters were able to contain the blaze and prevent it moving to other areas of the school.
Endeavour Avenue was closed for several hours whilst emergency services were at the fire and local traffic diversions were put in place.
Fire investigators will not be able to examine the school until later in the day when it has been declared safe to do so.
Investigators are still to determine the cause of the fire but believe it was well alight by the time emergency services were alerted.
Officers will conduct a canvas of local homes in the area in an attempt to locate witnesses.
Police have urged anyone who witnessed unusual or suspicious behaviour in the area recently to come forward.