I don't think they should be in high school libraries either. If the book depicts images of people blowing each other and graphic information about performing dominantly like your favorite porn star, then it doesn't belong in the public school system. There are plenty of ways to educate kids in a much more appropriate way than that. If you as a parent want to give your kid that type of content, then by all means do it but our public education system should not be in the business of giving kids access to graphic sexual content.
If there was a video library, the school wouldn't have an educational video with a graphic sex scene in it but they'll play mental gymnastics to ensure they can do the same thing with books. Both are inappropriate.