When Massey High School student Josh Tangimetua got an envelope with a letter from the school's youth support worker, he thought he was getting another detention.
Instead, it was an invitation to work with 12 famous artists on a project that has completely changed his thinking.
"I was a pretty bad tagger," he said. "I was hanging out with friends, wagging school, not even coming to all my classes, hanging out at the parks and stuff.
"But when this came around, I started changing my attitude towards it. It taught me that artwork is not to be used for illegal stuff, but to be used for amazing things."
Josh, 14, is one of 18 students who have worked with TMD Crew artists over the past four weekends painting a big water tank behind the school as TMD's 20th anniversary project.
Artist Jonny 4Higher, now 37, said the crew all started as graffiti artists, but most now had professional art careers in New Zealand, Australia and Germany.
Bobby Hung, 30, now teaches art at Unitec and has worked as an artist in Australia, Asia, America and Europe.
"I had a goal to paint in 30 cities before I was 30. I have achieved that," he said.
Their art on the tank looks indecipherable at first glance, but spells out words that mean something to the students such as "dance" and "empathy".
"Dance is a way of expressing myself, like graffiti," said Lennox Kaitapere, 15.
"It makes me feel cared for," said Josh, who doesn't know where his dad is and lives with an aunt.
Phoenix Peachman, 15, said he tagged "just to get known, to get your name up there".
Lennox said some mates "got kicked out from school. That's not the track I want to go down. I want to at least finish Year 12 and get qualifications to get better jobs."