Violent behaviour by children is on the rise and teachers are enduring assaults that have included kicks to the groin and a pencil in the eye, primary school principals say.
The Principals Federation and the Educational Institute (NZEI) said their members were reporting a growing problem caused by deprivation and family dysfunction.
But the Education Ministry said it was not aware of any research or statistics that backed up principals' claims.
Last week, Northland schools threatened to start suspending violent children because of a lack of support. The president of the Principals Federation Whetu Cormick said it was a national problem.
"I'm hearing from my colleagues across the country that they're at breaking point with the number of high behaviour issues that are in their schools," he said.
Mr Cormick said principals from all over the country had told him about assaults on themselves and on their staff.
"I've heard that principals have been assaulted, punched, kicked, kicked in the private parts, a teacher who was poked in the eye with a pencil who needed medical attention. Furniture being thrown around the room which has contacted professionals who work in the room."
Mr Cormick said for some children violent behaviour was a result of other special education needs.
"Young people who have got multiple issues including ADHD for example. We've got children who are suffering from various syndromes. We're also hearing about children who are anxious and some of them who have been diagnosed with depression."
Wellington principal Mark Potter said he had heard similar stories while travelling the country as a member of the NZEI's executive.
"We've always had children who've been challenging. It's the number of children that we have that is the big issue right now," he said.
Mr Potter said deprivation appeared to be the cause of the problem.
"It seems to be very much related to the growing disparities in our communities and society. So the more families that are under duress or under stress suffering from poverty the more you've got children who are actually experiencing those things and presenting at school with behaviours arising from that."
The principal of Manurewa East School, Phil Palfrey, said he had expelled two children already this year because they were too dangerous to have around other children.
He said the children did not have disabilities or special needs, they were simply violent.
"Sometimes other children have had to pull these kids off other children to stop them from getting worse. And that's with adults who are near who are paid to look after these children - these children can be so quick and so unpredictable that even a close adult can't get there quickly."
Mr Palfrey blamed bad parenting. "There's many factors, from the fact that they're sometimes on devices all day long, they're not getting enough sleep, they'll have parents who abandoned them. There are so many boys who don't have fathers or they have fathers who are just poor, poor role models. I'm just very sick of it."
Helping children depended on parents who were willing to cooperate and the problem area was those families who refused to do that, he said.
Mr Cormick said he raised the problem with the Education Ministry last week and he wanted it to get together with teachers, principals and other government agencies to figure out a response.
But the Education Ministry's head of sector enablement and support, Katrina Casey, said there was no hard evidence that schools were dealing with more children with behaviour problems.
Ms Casey said the ministry spent about $95 million on behaviour assistance for about 10,000 children last year, and that number of children had not changed much in the last couple of years.
The figure included children receiving help from the ministry's Severe Behaviour Service and from specialist teachers in learning and behaviour. In addition, schools had their own special education grants they could use.
The the Severe Behaviour Service received 2500 referrals last year, five percent or 111 more than the previous year, and 96 percent were approved, she said.
"That would tend not to suggest that there are major issues that require a significant increase in [the] Severe Behaviour Service," she said.
Ms Casey said stand-downs and suspensions for assaults had remained static for the past six years and a recent survey of secondary school teachers by the Council for Educational Research found student behaviour had become less of a problem.
She said schools should contact the ministry if they thought they were not getting enough help.
"If they have got cases that they think that we have not provided support for, then we need to talk to them about that. And often we'll find it isn't so much support the ministry can give, it might be us working in partnership with other services," she said.