Teachers say they are struggling to cope with growing numbers of children who are violent - and often still in nappies.
Two-thirds of 380 mainly primary and early childhood teachers raised their hands at the NZ Educational Institute conference in Rotorua when asked if they had been hit or assaulted by children recently.
Three-quarters raised their hands when asked if they were working with children with increasingly complex needs.
Teachers spoken to by the Herald said they had been kicked and bitten by students.
A behaviour specialist said many children were starting school without the social skills required to "self-regulate" their behaviour because their main interactions had been with technology, not people.
A rural primary school principal struggling to cope with a child who was not toilet-trained said she was "blown away" at a regional meeting where every principal said they had at least one child in nappies in their school.
"I'm the one who has to leave my own class and deal with these students because they are not toilet-trained and wee on the floor, refusing to leave the classroom," she said. "I have to remove them. They will kick me."
Teachers said there were not enough psychologists and behaviour specialists to help them cope with the growing numbers.
Kathryn Moss, a principal in a small rural school in Taranaki, said it took eight months to get Ministry of Education support for a child who had been to six different schools in another region until his "Mum couldn't handle him and sent him back to Dad".
"I have been in this area 22 years and both the severity of the behaviours, and the number of kids with behaviour problems, have definitely increased," she said.
"It's spitting, swearing, throwing objects, throwing objects at other children, ransacking classrooms."
She said the boy, who had been to six other schools, had never developed a relationship with any of his teachers and she was finally able to stop the violence when she developed a relationship with him.
"He said to me, 'You actually care about me and that makes the difference.'"
Mark Potter, principal of Berhampore School in Wellington and the person who asked for the show of hands at the conference, said many children had been passed around from house to house.
"The family is not there, necessarily," he said. "These kids are hyper-vigilant, always looking for something that to them feels like a threat, and their response to a perceived threat is often violence."
Levin East School principal Rikki Sheterline said parents themselves were struggling with increasing pressures from housing costs and poverty.
Whanganui Intermediate School principal Charles Oliver said the Ministry of Education provided "interim response funding" about 10 years ago to give schools some extra help with a difficult child for four or five weeks until longer-term behavioural support could be provided.
Ministry data provided to the institute shows that the number of primary school children given this interim support jumped by 41 per cent from 1512 in 2013 to 2134 last year.
There was a similar 43 per cent jump, from 1775 to 2434, in the numbers of primary and intermediate school children stood down from schools because of physical assaults on other students or staff.
But Oliver said there were now not enough behaviour specialists available to provide long-term support after a short-term intervention.
"It's not money that we want," he said. "It's experts to come in and give us support and advice."
Kindergarten teacher Helen Hansen said she has had problems with a boy since he started aged 1. Now aged 4, he is pushing other children around.
"We restrain him. While we are restraining him he's trying to head-butt you, bite you," she said.
She said that in theory the new Ministry for Vulnerable Children Oranga Tamariki could bring in support from other agencies, but she was unable to get their help because the boy's parents denied that there was a problem.
"It's heartbreaking. You have relationships with these children, you have loved them for a long time," she said.
"In an ideal world you'd have community hubs - people that come in and work with families and with children without needing parental permission."
An Oranga Tamariki spokesman said: "If a school or anyone has concern about the care and protection of an individual child they can contact us with their concerns and we will assess that child's situation and if there is need for a response from Oranga Tamariki."
Ministry of Education head of sector enablement and support Katrina Casey said the ministry understood that schools "face real challenges supporting children who have complex learning and behaviour needs".
"Last year we spent about $95 million on behaviour assistance for about 10,000 children. This includes children receiving help from the Severe Behaviour Service and from specialist teachers in learning and behaviour," she said.
"In this year's Budget, the Government provided an additional $69 million over four years to support children with additional learning and behaviour needs. This includes $34.7 million over four years to expand services for 1000 extra children with severe behavioural difficulties."