UPDATE: Police have confirmed six schools have been cleared after each received bomb threats around 12.30pm.
Police said each call was similar in nature and stated an explosive device had been left on site.
Local police attended each school and, along with senior school management, have assessed the risk and responded accordingly.
As part of the schools individual management plans some schools had already taken the decision to evacuate, and in some cases had sent students home early. Brookfield School in Tauranga was one of the schools evacuated.
By 3.30pm this afternoon, police were satisfied that there was no risk at any school and no devices had been found.
"Police take such threats extremely seriously," a police statement said.
"Given the undue alarm they cause and the disruption to school activities, we undertake a thorough response whenever threats of these nature are received."
Police are continuing their investigation into the source of the calls, however inquiries at this stage indicated the origin of the calls may be overseas.
Police were aware of very similar incidents occurring overseas such as Australia and the United States. These have involved recorded voice messages being directed towards schools in these countries.
"Because of this we are currently investigating whether today's events are the latest in this string of incidents and this will involve liaising with law enforcement agencies overseas."
Police thanked schools, parents and students for their cooperation while we responded to the threats made today.
3.51pm: Brookfield School has been given the all clear after a bomb threat this afternoon.
Principal Robert Hyndman said police gave the school the all clear at 2.35pm and no bomb was found.
3.19pm: Police are currently in attendance at six schools around NZ following calls which were made to each school of a "concerning nature".
The schools are Logan Park High School in Dunedin, Wellington High School in Wellington, Tamatea High School in Napier, Burnside High School in Christchurch, Central Normal School in Palmerston North, and Brookfield School in Tauranga.
Police are liaising with each school and the schools have responded in accordance with their local plans which in some cases included the evacuation of the school.
Police are currently assessing the nature of these calls.
1:51pm: Brookfield School principal Robert Hyndman said a caller made the threat to the school about 12.30pm.
The students and staff were all gathered on the school field.
About six police cars were at the school and a police officer was stationed at the gate.
Mr Hyndman said parents were being advised to pick up their children and take them home if they could.
Tauranga police acting sergeant on duty Adam Ramsay confirmed Brookfield School was one of six other schools in New Zealand to receive a bomb threat.
He said as far as he was aware Brookfield was the only Bay of Plenty school to recieve a threat.
EARLIER: Brookfield School in Tauranga has been evacuated this afternoon after receiving a bomb threat.
Police said all staff and children have been accounted for and have been removed to a nearby reserve.
"Initial investigations have identified that a number of schools around New Zealand have received threats," the police statement said.
Police were inquiring with respect to the origin of the threats.
The school is being searched prior to any decision being made with regards to persons returning to the premises.