Depends what you want.
The fundamental divide here is between those who feel that prison should be a punishment and those who feel that it should be an opportunity for rehabilitation. There is no cross over with these two arguments.
If it's punishment you're after then by all means lock them up throw away their key for an indeterminate period, remove anything but the basic stuffs required so that the inmate doesn't die then sit back in your chair and say 'That'll learn 'em'.
If you think the idea of removing someone from society and having them be a better person when they return seems like a good thing to you then giving offenders an opportunity to see that there's more to life than drugs and violence will probably seem like the way to go.
You can't have it both ways.
You're not going to get a 100 bright and shiny IT bods each year coming from these courses. What you might do is show some of them that there is another world out there. IMO, even if you only got 2 a year that went on to lead law abiding lives I'm guessing that the money you'd save dealing with the crimes they would've committed would more than make up for the cost of the courses. Doesn't that possiblity alone make it worth it?
If you think not you're obviously not thinking about society as a whole, which, whilst perfectly understandable, is a bit sad and depressing.