The lobby group Family First says figures show violence in primary schools has increased dramatically since 2000, with children as young as five assaulting both their teachers and other pupils.
Family First obtained the figures on stand-downs and exclusions from the Ministry of Education.
It says they show that last year there were 214 stand-downs for nine- year-olds who assaulted other students, compared with 133 in 2000.
The respective figures for 10-year-olds were 327 and 190.
Family First spokesperson Bob McCoskrie says the figures show that dangerous and violent behaviour is on the rise in primary schools, and that it has worsened since corporal punishment was removed.
Student behaviour will continue to deteriorate, he says, if pupils don't think there are consequences for it.
The Principals' Federation agrees that ministry data indicates that extreme incidents might be increasing, but its president, Ernie Buutveld, says a close reading of the other statistics shows some recent improvements.
Violence is also an issue in wider society, Mr Buutveld says, and the best outcomes happen when schools and communities work together to address problems.