Students at Ngaruawahia High School have been evacuated following a fire in the school gymnasium.
A fire and emergency spokeswoman said they were called to the school at 12.15pm to a fire on the outside wall of the gymnasium.
Principal Chris Jarnet said the fire was located in the girls' changing room.
He said the school was alerted to the fire when a student noticed smoke and warned a teacher.
"There was a class in the gym at the time but we managed to get them out pretty pronto when they saw smoke pouring out from one of the doors.
"One of the kids said there was smoke so the teacher had a quick check, opened up the door and found it black with smoke so got everybody out."
He said the school evacuation of students and staff "went like clockwork" and "the kids were really patient and everyone is safe".
Fire and emergency services were still in attendance at the school was trying to ascertain the cause of the fire. Four fire engines attended the fire.
"We are not sure of the cause yet but it looked like an electrical fire where everything goes all smokey," Jarnet said.
"There was really black smoke because of the wall linings and stuff you have in those places.
"There was no actual fire in terms of flames, it was just a lot of smoke."
He said the school gymnasium had recently undergone a refurbishment which cost around $100,000.
He was not aware of how much damage had been done as staff and students were evacuated from that area of the school.
"I am not allowed in there at the moment so I have not seen what damage has been done.
"They are just in the process of de-fuming and sucking all the smoke out now."
Jarnet said the school was in the process of rearranging the school programme so students could get on with classes.