Tremblay said that teenagers involved with the youth justice system develop friendships and peer relationships with others that have had brushes with the law.
“If you put a bunch of delinquents together, they won’t help each other; they will teach other,” he said. “They will try to one-up each other.”
The 20-year joint research project with the University of Genoa in Italy sought out boys from kindergarten who were at risk for delinquent behaviour, and who were enrolled at schools in the poorest neighbourhoods in Montreal. The researchers looked for impulsive boys with inadequate supervision and poor families.
Some 779 participants were followed from the time they were very six years old until they were in their mid-20s. Nearly 18% of the participants ended up with adult criminal records for infractions that included homicide, arson, and prostitution. All of those with adult records had spent time in the juvenile system.

See the full article from “Canada.com”