Whanganui High School is one of the schools in 12 areas around New Zealand that received a phone threat on Thursday.
A police spokesperson said they took the threats "extremely seriously" and
inquiries were being made to determine the source of the calls.
In a letter to parents and staff, Whanganui High School principal Martin McAllen confirmed the school had received an automated hoax bomb threat over the phone.
"Our staff immediately phoned 111 and three police officers arrived very quickly at our school.
"An urgent meeting was held and the situation was assessed fully with reference to our comprehensive emergency procedures.