Police have scoured Papakura High School in South Auckland after a bomb threat was made against it, but students were only informed this afternoon.
Two precautionary searches were carried out on the grounds and in classrooms by security personnel and senior police staff, but the threat was considered to be low level.
Police received a Crimestoppers message about a possible bomb threat but no other details were provided, the school has told students and parents in a statement.
Nothing was found and police determined the school grounds to be clear. The school has remained open all day.
"The decision to continue with classes as usual was made after consulting police who at no time considered our students or staff to be at risk," the statement from principal Simon Craggs said.
"I appreciate that you will be anxious about this event and the safety of your children. Let me assure you that their safety and wellbeing is my utmost priority and every decision was made with their wellbeing at its centre.
"I worked closely with police and the Ministry of Education to make an informed and considered decision to keep the students and staff safe on site and contained in a secure environment while Police carried out their precautionary search of the surrounding buildings."
Papakura High School will open tomorrow and it will be in contact with police in coming days.
A bomb threat was made last week against St Peter's School in Cambridge.
But police said there was no credibility to the threat after completing a thorough investigation.
"We are aware this was a distressing situation for the school, its students and parents," Waikato West Area Commander Inspector Will Loughrin said.
"We want to reassure the community, we take matters of this nature extremely seriously and any new information that comes to our attention regarding this incident will be assessed accordingly.
"Police will be providing ongoing support where necessary to the school and its community."