Fire crews were called to St Kentigern's School for girls in Remuera this morning after a fire broke out in the school's gymnasium.
A Fire Service spokesman confirmed the alarm was raised at 9.50am.
A Fire Service spokesman said five adults were being treated by ambulance staff for smoke inhalation.
He said five fire crews attended the blaze in the school's gymnasium.
The spokesman said the fire had been extinguished and had not spread to other buildings.