A government report into violence in schools has recommended that anti-bullying programmes be made mandatory - but a school association says this will do more harm than good.
The Ombudsman's Office yesterday issued its findings after its investigation into bullying at Hutt Valley High School in 2007.
At the time, police were called to the school when nine Year 9 boys were dragged to the ground by six older students.
The acting principal said then he had no regrets about how the incident was handled and "it wasn't an assault where somebody had spilt blood".
But the school's board of trustees yesterday apologised "unreservedly" for the way the incidents were handled.
"The boys involved and their families were let down by the school.
"The 2007 incidents were a hard lesson for the school. At its core, we did not look after the victims' and their families' interests nearly well enough."
The board said the school had changed its practices towards social education.
Ombudsman David McGee recommended schools' guidelines be amended to make anti-bullying programmes compulsory in schools.
"This is because the situation at Hutt Valley High School demonstrates that the lack of appropriate sanctions can contribute to, and risk normalisation of, a culture of violence."
He said a rigid national template for school discipline would have little merit, but the current "entirely discretionary" system risked producing arbitrary disciplinary decisions within and between schools.
Education Minister Anne Tolley said the report highlighted some serious issues but there had been significant changes since the incidents took place four years ago.
The Government had put $60 million into the Positive Behaviour for Learning plan.
Schools Trustees Association president Lorraine Kerr said schools already had systems, and a mandatory anti-bullying programme might do more harm than good.
"Based on the lack of action of one school, all schools are being charged with their mistake. In fact, every other school has had behaviour management programmes in place in one form or another."
"It's not a one-size fits all situation - what works in a school from a nicer area might not work for one from an area which has gang problems, for example."