New research by Otago University has found more than 60% of 15-years-olds binge drink on a regular basis, almost half have used drugs and a third had sex.
The results of the online survey have alarmed principals, who say more time needs to be spent on health education.
The survey's author Melissa Carter, who is a research student at Otago University, says the result is disturbing, but more surveys are needed to check it is not a statistical blip.
"I think many Dunedin parents and New Zealand parents as well will be quite shocked and concerned about these results," she says.
Of the 650 surveyed, 32% said they had had sex at least once, 61% binge drink and 47% have tried marijuana.
Principals say young people are growing up too fast.
"It's very difficult for them... the rate of change is so rapid that often emotionally and psychologically children can't cope," says principal Jane Johnson.
While the findings may come as a surprise to many parents, they are designed to help understanding of the issues affecting young people and how to address them.
"From here I'd like to see a national survey take place with the whole of New Zealand on an ongoing basis so we can monitor these trends and see if our interventions are having an effect," Carter says.
Already, limited historical data is proving an invaluable tool, showing that marijuana use among 15-year-olds has tripled in as many years.
"The youth do reflect society, they follow by example and in this day and age with changing social and family structures I think it's a reflection of that," Carter says.
