none! i don't believe in banning books.
also, on the topic, i went to an alternative high school for kids with emotional issues. we were all smart kids, but our lives were such a mess that we did not have a lot of motivation to do schoolwork on top of everything else we were dealing with. the teachers were always looking for ways to get us more interested in our schoolwork, so one year in english class, we were given a long list of books banned in libraries and schools all over the u.s. and we could pick books from the list to read and report on. it was a really cool assignment and it got us all interested in reading as well as class discussions about the idea of banning books. many of us were surprised by a lot of the books that had ended up on the list too. but i'm really grateful i went to a school that was open minded enough to let us do that.
AND my last year at the alternative school, the school was bought out by a similar school with similar teaching methods. it was a larger school for younger kids, but their missions were similar and the other school had tons of money which has since been used to greatly upgrade the school i went to. i graduated before the money from the other school helped upgrade mine, but one thing the other school did for us my last year there, and i believe they still do, was around the holidays, we were told we could ask for ANY book under like $35 and they would buy it for us. i remember half of my classmates asked for books that seemed "inappropriate" and i don't think any of them really expected to receive them, but when the day came, we all got the books we had asked for. i asked for SARK's journal and playbook, so i figured i'd get that anyway, but some kids asked for books of nude art, the theory behind the word "fuck", all kinds of stuff. it was a fun experience. so yay for all books. don't ban them