Criminals now seem to find it a privilege to go to prison, because they know they get luxuries. That should not be the case, it should be somewhere that they fear to go - there should be no luxuries, no TV, no nice food, no games. The vast majority of criminals that come out of prison just re offend, so it evidently clear that current rehabilitation methods do not work; this is likely because they aren't in prison for long enough
I am a strong supporter of the US Justice System. Here in England if you murder someone, but you are good in prison - you get let out early. No matter how good you are - you MURDERED someone, I think that deserves no forgiveness and you serve the full sentence you are given. Criminals know that if they are good they can get out earlier and just go and commit the very crime that they went in for.
There should very little socialisation between high level criminals, as that is when they start to organise drugs coming in, and they establish gangs - leading to violence in prisons.