It has written to its members telling them to consider refusing Ministry of Education directions to accept such children unless they are certain they will get enough support.
The federation, which represents hundreds of primary and intermediate school principals, has been complaining for several years about a growing number of students it says are traumatised by their home lives and who pose a danger to other students and to their teachers.
The federation's president, Perry Rush, said schools were not getting the help they needed to safely include violent children in their classrooms.
"There is a national outcry at the moment, a national call for help from principals who are experiencing just being in the vice between the ministry's requirement to have these young people at school and the damage that these young people are causing to the wellbeing of young people and their teachers," he said.
"Even though it is a legal expectation for those young people to be enrolled if they are directed, there is a really important conversation to be had with the ministry around the appropriateness of such placements."
Rush said schools also had a legal requirement to ensure their workplaces were safe and some children would be better off in alternative education arrangements that would help them work through their problems.
"These are young people who are really traumatised. Many of these cases involve young people hurting other young people at school, that can be physical harm, emotional harm. There are instances where young people have used weapons at school and weapons towards staff and other young people, and there are young people who have damaged classrooms and equipment, throwing classroom furniture around."
Rush said the federation was currently supporting a school that was refusing to accept a child excluded from another school for assaulting a classmate.
"This child has used a weapon towards other children and we would judge that to be a very serious concern. Is it appropriate for that young person to be directed to another school to be enrolled alongside other young people and teachers," he said.
The president of Te Akatea, the Māori Principals' Association, Myles Ferris said principals had learned to push back against the ministry in order to get more help.
"While we would never advocate too strongly to defy the law, when the law's an ass we support that we need to push back until we get the resources and support that we need," he said.
"The experience that I've had is that when you push back against one of these things when the ministry tries to strong arm you, you actually get more support. They start realising that you're not going to just roll over, then they start looking at ways that the ministry can support the successful transition of that child into the school."
Ferris said some children were damaged by past experiences and needed a lot more than just a few extra hours with a teacher aide.
"We are not dealing with the causes of that behaviour, we are trying to manage that behaviour. We know that the behaviour stems from a level of trauma, that fight, flight or freeze instinct that children have to protect themselves. Even when they're lashing out that is usually a very strong sign that child is in trauma and the need for additional support," he said.
Ferris said the ministry needed more educational psychologists who could work with children in school and in their homes.
The president of the Secondary Principals' Association, Deidre Shea, said secondary schools sometimes refused to enrol a violent student.
"Legally of course we can't refuse but certainly I am aware of situations where there has been significant push-back by the school in terms of if there has been a situation where it was felt that it was not safe," she said.
"I'm aware of situations where the student has not enrolled in that school and another avenue has been found."
The ministry's deputy secretary sector enablement and support, Katrina Casey, said the Principals' Federation's stance was concerning.
"Every child and young person has a right to an education and we are concerned that NZPF is encouraging its members to exclude a child from attending school," she said.
"Use of the power to direct is a very last resort and one that we do not use lightly."
Casey said there was a small number of children with very challenging behaviours, often due to social factors associated with their family.
"When decisions to direct an enrolment are made, our regional staff will work through what's best for the student with the school, the students whānau and other agencies," she said.
Casey said the ministry could provide support for enrolling such students including transport, in-school activities, and additional learning support.
