I found out he got jumped in there, some boys jumped him as he sat & watched Tv
When you speak to the case manager I would ask what she/he believes motivated the attack? Is this gang related? Is it racial? Does your son owe a debt? Is his behavior in any way out of line? Was there a dispute with a certain individual?
There have to be reasons this has happened. And the reasons are important to determine next steps. Attacks like this don't come out of nowhere. They have reasons.
Finally, that case manager is responsible for making decisions to keep your son safe if there is continuing risk. I would interrogate this person to try to evaluate yourself, JUST WHAT IS GOING ON.
Does your son require protective custody?
If the person does not give you answers that are sufficient for you to understand and do your own risk assessment, I would go up the chain of command. I am only familiar with prisons but there the chain of command is like the military. If you can't determine who is this person's boss (assuming you are not satisfied with what they say or do) I might go to the top, in prison that would be the warden, if you still feel there is inaction. After that, in prison, would be to go to the Department of Corrections in the State Capitol. Believe me. This kind of thing works. Family members do it all of the time.
I want to add one more thing. I realize you believe your son has changed, and I'm sure you're right. But incarceration is not real life. Once released freedom and temptations and the status quo and peer influences have great power. Prepare yourself for the possibility of backsliding. Al Anon helps people to deal with situations over which they have no control. Or any 12 step group.
Take care.