A fire broke out at Pakuranga Heights School on Sunday night just hours before school reopened after a term break this morning.
School authorities were informed of room 23 on fire at around 9.45pm on Sunday.
Crew from three fire brigades handled the fire blaze till 1.30am.
Students walked into school this morning to find a room completely gutted and the neighbouring classroom cordoned off.
While principal Fintan Kelly was busy helping the fire fighters to investigate the cause of fire, a school spokesperson said that students from the two classrooms had been accommodated in other classes.
“Luckily it was a standalone building so the fire was contained. The cause of fire is undetermined as yet,” she said.