I think them working a hard day to earn there keep probably gets them pretty tired so they get a good nights sleep, i think that provides a better environment for the guards. And its better then having them in a cell 23 hours a day trying to make a tooth pick into a weapon or thinking of ways to harm others inside the system.

You also think they would be angry and take it out on society, I think they might think twice before doing something to get them back in the poke.

I personally don't think whats going on in the prison systems we have now are all that great. But will agree that some form of education can't hurt any inmate.

Also when you referred to chain gangs not working in the past, they were also beaten and whipped, withheld water and food . Kinda comparing apples to oranges. But I just aint that smart so I am probably wrong.