Which is probably the right way to go about things. When you're dealing with minors, the important bit is how they respond to books, music, movies, etc. rather than the actual content itself. (I suppose that's true of adults too, but children have much less life experience to suggest what does or doesn't fit within acceptable social norms.)

Unfortunately, when it comes to education factories the ability to judge how a child is responding is much more difficult. That's not too surprising since teachers simply have far too many children to keep track of, so it's harder to judge how a child is relating to the work. Speaking as a teacher, it is easy to figure out for some children but very difficult to figure out for other children. Making life more fun: different kids will respond to different teachers in different ways, so you can't rely upon the research to tell you which is which and thus who to watch out for. Ultimately that means that teachers have to take a more conservative approach in judging what is and isn't appropriate reading. Sometimes we'll loosen the reigns for students who we know better, but only when we know them well enough.

(On the flip side, I taught teens math in another life. We had a "Drop Everything And Read" period during one math class. It was the easiest literacy course that I ever taught. I'd bring in a stack of readings ranging from newspapers to novels, then let the student choose. I'd also sit and read myself. No analysis. No grading. No judgement. It all worked so much better than a real language arts class.)