Who should decide which books are suitable for young people?

If there was a book that a large number of parents simply don't understand why it's included on a social studies reading list, then I think that the teacher or principal should be expected to explain why it is included.
There would be no reason why a teacher or principal would be able to just tell the parents why it is on the list. If it was just a book that was telling about history then it should be fine to tell them. I also think that the parents shouldn't get mad because it is after all a history book. If the is shows violence, that is all a part of history.

I understand that some parents would want to block out or completely get rid of the profanity. But on the other hand, a bunch of kids are using profanity and their parents are okay with it. Also, at a certain age, kids are old enough to see and hear it. They will hear and see it in the future so what difference does it make if it comes to them now.