I think checking out any* book, without a parent's explicit consent, is potentially subverting the parent/child relationship. Families are unique - there's no clear agreed upon standard of which books are "good" and which books are "bad." And without such a standard, it is, in my opinion, the library's responsiblilty to make literature and information as accessible as possible with few, if any restrictions. It's not the library's responsibility to choose which books are somehow "appropriate," that's the parents' job. And if kids are sneaking out to library behind their parents' back, idk, that seems pretty wholesome. Seems a lot better than sneaking cigarettes or booze or whatever.