An email from Hutt Valley High School says a person on a fake social media account is encouraging teens to share nude images, and when they do, then threatens to post the pictures publicly if they do not send money.
"An unknown individual is reportedly targeting teenagers in the Hutt Valley area through online platforms like TikTok.
"The perpetrator or scammer has created a fake profile to build trust and manipulate young people.
"As trust develops, the perpetrator shares nudes supposedly of themselves and encourages students to reciprocate. Unfortunately, the situation has escalated into exploitation, with the perpetrator demanding money under the threat of exposing these photos publicly."
School principal Denise Johnson listed seven steps for parents if they fear their teenager has fallen victim to exploitation.
Some of the advice includes reporting the incident immediately to police, staying calm and supporting the teenager and to block the perpetrator.
Netsafe chief online safety officer Sean Lyons could not tell RNZ whether the school had contacted them out of confidentiality, but said the email sent out was comprehensive.
"It's good to see schools putting that kind of information in the hands of parents, they're obviously concerned. Sextortion is something that schools, that parents, that we should all be concerned about so it is really encouraging to see schools taking this step proactively and supporting their students and their families," Lyons said.
He said cases of sextortion in New Zealand had increased in the past five years.
"We've seen an 88 percent rise in sextortion complaints to us since 2019, it is something that we see frequently, it's certainly something that's affecting New Zealanders, young and old and that numbers on the rise," Lyons said.
The school's principal declined an interview with RNZ.
RNZ also approached police, who said they could not talk about specific cases.
