I don’t have much first-hand experience, but our penal system for youth and adults is far from ideal. These people have gone astray from our society’s values for one reason or another, and are sent to a place where most of the people they are interacting with have also gone astray. This environment is not conducive to any sort of rehabilitation for the offenders. They make ‘connections’ and exchange stories about how unfair life and the system are, and how glorified a criminal lifestyle can be.
If someone is genuinely remorseful when entering prison, and truly wants to turn their life around, it is difficult for them to find support and they may even get harassed by the more hardened criminals for being soft. You have to blend in, at the very least, in order to survive. For juveniles, there may be somewhat more resources available to them to get an education or perhaps learn some trade, but the kids going in there usually have such a big chip on their shoulders that they aren’t about to utilize those options.