Fire crews have been called to the Colo Vale Public School after smoke was seen coming out of the administration building.
They arrived around 6 last night, but there was no actual fire.
Southern Highlands Rural Fire Service Inspector David Stimson says the large amount of smoke was caused by a distribution board which was overheating.
Fire and Rescue NSW were also in attendance along with Endeavour Energy who made the area safe.
The operation was wrapped up by 9pm.
Mr. Stimson says it's an important reminder for local residents not to overload any power points or extension cords.
IMAGE CREDIT: Colo Vale Public NSW Government