The Fire Service is treating a fire at Hokowhitu school in Palmerston North as suspicious.
The school's gym equipment shed was ablaze when crews arrived at 5am on Sunday. A large wooden seat nearby was also alight.
Senior station officer Graeme Mills says unfortunately it is common to be called to fires on school properties over the summer holiday period.
It was the third such incident at a school since Thursday. The other two were in Auckland.
The Fire Service says a fire at Maungawhau school in Mt Eden at around 2.30am on Thursday was deliberately started. The school hall was badly damaged.
There was also a suspicious fire at about 8.30pm on Friday, at the Flanshaw Road School in Te Atatu south, Waitakere.