A fire destroyed the woodwork block at Whangamata Area School this morning.
It took firefighters in eight appliances from Whangamata, Opoutere, Pauanui, Tairua and Waihi at least an hour to bring under control, north fire communications shift commander Scott Osmond said.
The fire service was called to the blaze about 11am.
Woodwork teacher Bob Pipe said the woodwork room was locked at the time and no one was inside when the fire started.
Principal Ross Preece said everyone was "fine" and it was fortunate everyone was out on the sportsfield at the time.
He said a staff member had been in the workshop building at the start of the day but it had been locked ever since.
More than 20 firefighters are battling a large blaze at Whangamata Area School.
Fire service northern communications centre shift manager Scott Osmond said a school building about 25 metres by 10 metres was well involved when firefigters arrived.
The fire service was alerted to the fire on Port Rd about 11am.
Five trucks from as far away as Pauanui and Waihi were still battling the blaze and will be for some time, he said.
No one was trapped or hurt.