I'm going to prison...

They can't watch a movie because real-life experience is a better teacher than any film or classroom can ever be. With a movie, you don't get all the sights, smells, tastes, sounds, and feel of the area - you just get what the documentarian wants you to see (usually a watered-down version of the subject). Also, in-class speakers are frikking boring. The students aren't going to learn much about prison from just being talked at.

Also, to all of you talking about the psychos in prison, the vast majority of them (convicted for lesser crimes) just want to do their time, be good, and possibly get out on parole for good behavior, and put that whole place behind them. Only a very few are still "bad".