Some people hold an opinion that sending criminals to prison, nowadays, does not help them adjust their mind visibly, but education and job training might be able to. However, on my personal level, criminal should be blamed for their crime by limitation of civil rights by staying in prison. Meanwhile, education and job training should play a significant role in prison to ensure their behavior and living after leaving prison.
First of all, prisoner might intensify their hatred under strict regulations, especially unfair treatment. Once they suffer from ill-treatment, for example beating by policemen or other prisoners, the powerlessness in prison will lead to the abuse of violence outside. Also, it is the intense desire for liberty that could make them much more extreme and aggressive. What's more, perhaps, they could find some people with similar minds, gather around a small group and strengthen crime awareness of each other.
Secondly, without prisons that limit criminals' behavior, it is so hard for managers to educate them and get them job training. Most prisoners, obviously, are adults which means their minds have already grown up and are hardly changeable. Therefore some appropriate compulsory measures are necessary to let them calm down and do learn something.
Finally, after several years separating with the world which is developed rapidly and changed all the time, prisoners will be failed to adjust the whole new life. In The Shawshank Redemption there is a line, "These walls are kind of funny like that. First you hate them, then you get used to them. Enough time passes, gets so you depend on them." What we need to do is, via job training, to make them independent from such walls rather than relying on that walls.
In short, punishing criminals, educating them and making them a better life, there are 3 priorities, prisons should set. What we want to do is not destroying all the criminals but improve their moral characters and, consequently, enhance our society.