Firefighters have been battling a blaze at Hamilton school overnight.
They were notified about the fire, at Sacred Heart College, just before midnight and 14 appliances were dispatched.
One of them, station officer Darren Bowler, said he could see a glow in the smoke from a distance as he approached the school and when he got there saw it was well alight.
"There were a lot of flames, broken windows at the top, a lot of smoke," he said.
Mr Bowler said two classrooms at the end of a wing were alight but firefighters were able to stop it spreading further.
Several other classrooms would be damaged from smoke or water, he said.
The cause was not apparent but a fire investigator was already on the scene, Mr Bowler said.
One crew was still on the site in case there were any flare-ups.
Sacred Heart has posted a note on its Facebook page asking people to stay away for the weekend.
It said no one was hurt and thanked the emergency services.
Detectives and fire investigators are at the school trying to establish the fire's cause.
Acting detective sergeant Ian Foster said they would like to talk to the people who were lighting fire crackers near the school last night.
