For one of my graduate courses, I am writing a research paper that dives into the issue of profanity and young adult/children's literature. I have to say, this has been an inspiring topic to research, particularly when it comes to how librarians handle challenges to literature.
Between pulling, burning, and censoring books, the most interesting technique has definitely been the permission slip tactic. Really, I would LOVE to see how a modern high school librarian deals with that. To be quite honest, once that item has left the library the librarian loses control of the item. That book can get read by anyone, not necessarily the person who checked it out. So, does the permission slip tactic really "fix" the issue?
It's kind of like that with a lot of things. Isn't it slightly human nature that if someone tells you that you can't do something, it just makes you want to do it more?? Really, I truly believe that the best thing parents who are worried about a book can do is communicate with their child. Encourage parents to read the book first, and take a look at issues that might come up. Have them talk with their kids! Sometimes, controversial books about tough topics can spark meaningful conversations that parents should be involved with.
So, really, the permission slip tactic might just make it harder for a kid to have access to a book, but that doesn't mean they won't get access somewhere else. Parents should look at the situation as an opportunity to discuss their values with their kids.