The Lake Country Fire Department responded to a fire in a science classroom at George Elliott Secondary School around 10 p.m. Friday night.
When crews arrived, there was light smoke in a hallway, and water coming out from under a classroom door.
Inside the classroom, they found a fire had started in a waste-paper basket and spread up a wall, setting off the automatic sprinklers.
The classroom where the fire started sustained heavy smoke and water damage.
A classroom next door was also damaged, to a lesser extent.
A restoration company was called, and janitors at the school began the cleanup.
Lake Country Fire Chief Steve Windsor said without the automatic sprinklers, the damage to the school would have been much worse.
The fire is not considered suspicious.