Some state prisons have a scared straight program…look into it, they work. My dad was a cop, and then a probabtion officer, we had troubled teens in and out of our house all the time, even had foster sister. He even brought home a convict for the weekend on work release, he was in for murder. Anyway, they need a person that they can talk to that they respect and that they knows respects them. They need someone to set the rules and KNOW that if they screw up then it’s their own responsibility.
Check with the probation office in your area, and go in and talk to the cops, they will help. But the best is getting them into a state prison, where they live for a day, sometimes a whole weekend of what they are headed for.