Police officers have been called into primary schools where boys as young as 8 had taken secret photos of girls getting undressed and posted the pictures online.
A growing number of primary school children are now seeking help from unwanted cyberbullying attacks - and those harassing them are likely to be the same age.
Psychologists, internet safety experts, educators and police have voiced alarm at the number of youngsters involved in online bullying and sexual exploitation.
West Auckland school community officer Senior Constable Paul Stanko said he had been called in to several primary schools after 8-year-old boys had cyberbullied their peers.
"There's been cases where inappropriate photographs from school camps, boys trying to get pictures of girls undressing and that sort of thing, have been posted online and saying silly things where they've not realised what they are actually saying."
Mr Stanko said in these cases the emphasis was placed on educating the youngsters to behave differently.
"I speak to the whole school - the children aren't often singled out but the classrooms are together - and if necessary I'll speak to the parents as well and give advice."
Crisis help agency Kidsline said children as young as 7 were now phoning for help with cyberbullying.
Chief executive Jo Denvir said it was a national shame, with very few boundaries in homes for young cyber citizens and adults providing a poor example of how to behave online.
YouthLine psychologist Bridget McNamara said more girls than ever, aged between 11 and 14, were seeking help over sexual exploitation.
NetSafe's Martin Cocker said a number of advisory groups in the schooling sector were reporting a growing number of cyber harassment and bullying incidents involving children from intermediate and primary schools.
Many children were copying older siblings and celebrities and sending naked selfies on social media.
"The sharing of those is really quite common among youth, and younger children see that behaviour from their older siblings or from other media figures," Mr Cocker said.
"Once those images are created then shared with another audience you've got everything required for harm to be done to that child."
He said young children were also drawn into difficult online relationships with exploitative older people.
Online Advisory Safety Group spokesperson Patrick Walsh said the prevalence of pornography had had a hugely adverse influence.
"Students as young as 12 are exposed to explicit pornography and some of that's quite violent, so they grow up at those critical ages when they're forming relationships thinking the sort of behaviour they see on the web is actually normal."
This is echoed by New Zealand Intermediate and Middle School president Doug McLean: "It's getting younger and I think the worrying thing is some of the stuff that kids are looking at is desensitising them.
"Parents should be aware of what their kids are getting into."
Hard core feel 'entitled'
School leaders are worried that a small but defiant group of high school bullies are headed for the courts.
The Online Safety Advisory Group - which has representatives from secondary schools, police, Netsafe, the Children's Commissioner, Human Rights Commissioner, Crown Law and the Ministry of Education - provides guidance for safe school online strategies and handling incidents involving cyberbullying.
Advisory group chairman Patrick Walsh said online abuse by school pupils remained an extensive and growing problem.
"We're still getting complaints of cyberbullying, sextortion, sexting," said Mr Walsh.
"There's a small group that are resistant to attempts to stop them from cyberbullying and those students will ultimately be dealt with under the Harmful Digital Communications Act."
He said schools were focused on tackling the issue through education in a carrot and stick approach.
"The carrot approach works with most students but [there is] the small group that just continually resist any attempts to change their behaviour. It ... tends to be a group of young males, who think that they have an entitlement to harass [others]."
But it remained a minefield for schools, with blurred jurisdictional issues over bullying taking place out of school hours and parents reluctant to see their children exposed to the justice process.
"Often [girls] who are ... evident victims of ... sexting and sextortion don't wish to lay a complaint or are not very co-operative."
New Zealand Principals' Federation president Iain Taylor said it was not helped when parents deliberately hindered investigations.
Some [parents] just don't want to get engaged."
Mr Walsh said latest research and what was working was to develop in teenagers a high level of empathy.
"If they can ... put themselves in their shoes and feel what they're feeling it's less likely they'll bully."
Where to get help:
• In an emergency: call 111
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633, or text 234 (available 24/7) or email@example.com or live chat (between 7pm and 11pm) http://livechat.youthline.co.nz/mibew/chat?locale=en&style=youthline
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155 (weekdays 11am to 5pm)
• NetSafe: 0508 NETSAFE (0508 638 723), www.theorb.org.nz