In Otago, Waitaki Girls’ High School in Oamaru, Wakatipu High School in Queenstown and Dunstan High School in Alexandra were affected.
An email from Wakatipu High School sent to caregivers said pupils were evacuated due to a call warning of a bomb threat, which was believed to be automated and from an overseas number.
The school had been advised by police there had been more than 20 such calls to schools around the country both yesterday and in preceding days.
Classes at the school resumed after it was decided the call posed no credible threat, the email said.
A statement released by police about 12.30pm said inquiries were also under way in relation to threats at schools in Masterton, Kaikoura, Greymouth, Levin, Whanganui, Rolleston, Takaka, Geraldine, Ashburton and Palmerston North.
The threats were taken seriously but police did not believe there was a safety risk and officers were making inquiries to determine the source of the calls.
The schools involved were thanked for following their emergency procedures, as were the wider school communities for their co-operation, the statement said.
At Wakatipu High School, pupils were evacuated into a field and two Fire and Emergency New Zealand appliances could be seen in attendance along with police.
Waitaki Girls’ High School principal Elizabeth Koni said the school was advised by police to evacuate while officers did a sweep of the school.
Pupils returned for afternoon classes after being given the all-clear at 1pm, Mrs Koni said.
Dunstan High School deputy principal Todd Adams said pupils evacuated while police searched the site for suspicious items before pupils returned to learning.
Caregivers were notified at both schools.
On Tuesday, police said in a statement they had responded to threats at five North Island schools in Waikato, Thames and Gisborne. — Additional reporting Lucy Wormald, Rebecca Ryan and Shannon Thomson
