We ran into some difficulty last year when my DS was a first grader was interested in anatomy. He had been given free access to the library and came home with a book about how to deal with the bodily changes that accompany puberty. The book discussed issues like how to deal with comparing genitalia in the locker room and how to deal with hair growth on specific parts of the body. We had to ask the librarian to monitor his reading a little more closely because he read the entire book before he arrived home from school.