The assault laws need changing to protect teachers acting in good faith, says the President of the Tai Tokerau Principals association.
Pat Newman says the case of a principal who was investigated by the police for three months for restraining a boy was a threat to all teachers.
The principal in question had gone through hell, even though he had acted within Ministry of Education guidelines based on the law, says Pat.
He had been grilled by the police for three hours and they had subsequently interviewed many of his friends and colleagues which has put him under enormous stress.
In the end, no charges were laid.
The police told RNZ they had to investigate such complaints thoroughly.
But Pat says the length of the investigation was unacceptable.
"There is no argument that they should investigate if a complaint goes in.
"But should it take three months? And the second thing is, I don't think the law is adequate."
The law should give teachers the right to act as any parent would, in restraining a child who was trashing a classroom or trying to run away, says Pat.
"We used to have the in loco parentis provision - but we lost that years ago. So now we have the situation where you can't physically stop a kid running off or destroying property. Only if it's likely to hurt another person can you touch them."
Pat says he had recently been forced to restrain one girl five times recently and the only reason he could step in was because she was hurling blocks, which had the potential to injure.
He says that was the sort of judgement call teachers were now loath to make.