As news of the fire spread, teachers and students began to arrive at the school.
Principal Doug McLean had just arrived at the school when the Rotorua Daily Post caught up with him.
"I'm shocked and angry after being told the fire was deliberately lit," Mr McLean said.
"I'm not too sure what's going on yet or how bad the damage is - I was told it was in the RTLB (Resource Teachers: Learning and Behaviour) class and that's about all I know at this stage."
He said the school would undoubtedly be working hard to ensure everything was as close as possible to back-to-normal when students returned after their holidays.
One teacher, who did not wish to be named, fought back tears as she said it was the worst start to the school holidays.
A fire service communications spokesman said one classroom and an adjoining building were badly damaged by the fire and an investigation was underway into its cause. He could not confirm that the fire was deliberately lit.