Girls are overtaking boys as the biggest bullies in many school playgrounds, reversing thousands of years of male-dominated violence.
School counsellors say girls have become more violent in the past 15 years and boys have become less violent, apparently reflecting feminist messages in popular media.
The reversal is dramatic. Only five years ago the Youth 2007 survey of 9100 secondary school students found that only 2.9 per cent of girls, compared with 6.8 per cent of boys, admitted to bullying others at least once a week.
Last year, 11,000 females of all ages, compared with 38,000 males, were caught by police for violent offences.
But Bill Hubbard, a guidance counsellor and now deputy principal at Rosehill College in Papakura, says girls are now physically violent too.
"Years ago, the spectrum of girls' bullying behaviour was narrow. It was making verbal comments, writing notes, possibly pulling hair at the very most," he says.
"Now they have expanded to fill the entire spectrum, including the violent end which only boys exploited in the past. I've seen that in 15 years.
"I think what has happened is that the amount of high-end violence by teenage boys is actually less - boys have come down and girls have come up . .. In some schools, and in some countries, it has even overtaken boys."
Mr Hubbard, who wrote a thesis on the "undercover teams" he created to handle bullying, points to films and TV shows that portray tough women handing out as much violence as men.
"I think females have increasingly broken the ceiling in all areas of life, and unfortunately they have broken the ceiling on violence too," he says.
"I think what is happening is that boys used to do the heavy work for girls - the physical stuff might be in defence of girls.
"Nowadays, because the girls are prepared to do that themselves, boys stand and watch."
Karyl Puklowski of the Auckland Alternative Education Service says her service sees increasing numbers of girls who are physically violent.
Mike Williams, guidance counsellor at Edgewater College in Pakuranga, says: "We see girls being much more involved in this relational violence than boys. I think bullying is actually more common among girls than it is among boys."
But Glen-Paul Waru, who tutors teenagers at Quality Education Services in Mangere, says boys still think it's wrong to hit girls back.
"Some of the girls can get physical, and they take it out on the boys, knowing they won't get touched," he says.
"The boys know they can't touch back, so they are resigned to being bullied. You can see their self-esteem really drop."