It comes after the 2013 Roast Busters scandal involving a group of West Auckland students using Facebook to brag about their sexual exploits with intoxicated, often underage girls. One was as young as 13.
Dr McGregor said it was a huge problem, with about one in four girls and one in eight boys affected by sexual violence in New Zealand before they hit their teens.
"Rather than stigmatise Opotiki or even West Auckland where the Roast Busters were, I think it's important the public know that probably every school in the country is dealing with sexual violence whether they know it or not," Dr McGregor said.
"It's so hard for people to disclose sexual violence ... I'm feeling for the young people and their families, who are affected by sexual violence, they'll be going through a very, very difficult time at the moment."
She said progress had been made since the Roast Busters case - including more police training, Government lobbying and sexual prevention pilot programmes introduced in many schools nationwide - but there was still more to be done.
It was important for young people to be taught about their rights and responsibilities as well as how to negotiate consent, Dr McGregor said.
Social media was a danger, with sexual violence films being easily uploaded online - but it also meant more young people could speak out, she said.
"We know that young people don't usually report to counsellors or police, and often they don't report to their families first. Usually the first person they tell is their best friend. So we also have to educate our young people how to help a friend.
"I think there are added dangers for our young people because they can post the filming of sexual violence online, so the humiliation and the shaming can continue but there's positives as well. I think it goes both ways."
It was understood some of the Opotiki victims may still be attending school with the alleged perpetrators.
An "online component" involved was understood to be a private Facebook page, TV3 reported.
