Why is school so much like a prison?

A student once told me that school was like a prison. They tell you when to eat, when to drink, when to use the restroom, when to sit, when to stand, what to say, what not to say, how to think, what to learn, how to dress, who to hang out with, etc.

Is the student right? Is school like a prison? If it is, what other aspects are similar to a prison? Why would this be the case? (Really think about the motives of the adults who create the school system. They probably have a good motive, so what is it?)