Boarding pupils at Truro School were evacuated on Thursday evening after a fire in a deep fat frier.
Two fire appliances from Truro Community Fire Station were called out to the fire in a kitchen.
With firefighters wearing breathing apparatus using one hosereel, foam and a thermal imaging camera to extinguish the fire by just after 6pm.
The firefighters remained on scene for a further one hour and no one was injured in the fire.
Everything was reported to be back to normal on Friday, with meals are being prepared and served as usual.