Thousands of children are being kicked out of school for possessing drugs, with one principal saying he regularly has supermarket bags in his office that are full of confiscated cannabis.
The number of exclusions and expulsions in primary and secondary schools increased nationally between 2008 and 2012.
Figures released under the Official Information Act show Auckland leads the way for school drug abuse, and Northland isn't far behind.
At least one principal in Northland had a supermarket bag full of confiscated marijuana in his office at any given time, Principals Federation president Phil Harding said. "I've spoken with a primary-aged child who knew where dad's stash was and dad didn't know he knew.
"Schools are mopping up the behaviour of these kids that is being modelled by the parents."
In another case, a 17-year-old who had been addicted to drugs for three years was told by his "well-to-do parents" to pack his bags and leave.
"This is two parents who loved their son, but things had got so bad they had to say 'get out' in order to make him turn things around."
Ruth O'Neill, principal of Cannons Creek primary school in Porirua, said Auckland probably led the statistics simply because it had a high number of low-decile schools.
There are 14 decile one colleges in New Zealand, of which eight are in Auckland and only one, Porirua College, in Wellington.
O'Neill said low-decile schools spent a lot of their time teaching students good behaviour. "They see and hear a lot of swearing, abuse, drugs and bad behaviour at home, so we spend our whole time trying to teach them how to behave at school."
Wainuiomata High School said it dealt with one or two incidents of drug abuse each term - significantly more than cases of alcohol abuse. "There's been a real shift with alcohol and we now discipline about four times as many students for marijuana than alcohol," principal Martin Isberg said.
"Marijuana is freely available in most communities, so the numbers aren't surprising."
The number of students being disciplined for drugs tended to depend on the number of drug dealers in the community, he said. "It comes and goes, and just depends on how many people are dealing."
At Naenae College, the number of expulsions and exclusions had fallen in recent years because of a new focus on restorative justice, principal John Russell said.
Parents were encouraged to visit the school when their children misbehaved, and to set boundaries for them.
"We form a contractual agreement for behaviour change that must be met before they can return, which means we hold that door open longer for them to return."
- The Dominion Post