Students at Bernie Custer Secondary School are off Tuesday following a fire Monday afternoon in a second floor washroom that Hamilton Fire has deemed suspicious.
Firefighters say the incident happened just before noon and prompted the evacuation of students and staff.
One student was sent to hospital for smoke inhalation.
Special education students were moved to a nearby community centre until transportation could be arranged.
Hamilton Fire says there was extensive smoke causing close to $250,000 worth of damage.
In a release late on Monday, the Hamilton Wentworth District School Board said damage was still being assessed.
Some classrooms are expected to be relocated due to the damage when classes resume on Wednesday.