Unfortunately the prison system is more about making money than rehabilitating people. It's also over-crowded with people who have low-level drug charges, addiction problems, non-violent thefts, and hosts of other reasons that they shouldn't be in there - which in turn makes any rehabilitation efforts that do occur very minimal.

That said, the minute you stick a gun in someone's face, prison is where you belong. Especially if you pull the trigger. These kids were willing to murder someone because they couldn't get access to a relatively small amount of cash. If they were willing to do that, they are probably already counting on crime being the only way to support themselves. They belong out of society.