This is what I sometimes hear as I tell the 1st, 2nd, even 3rd graders that even though it took all their muscle to heft Harry Potter and the Deathly Hallows onto the check out counter, I am not checking it out to them. I don't like to censor what the kids check out, and even if they are "advanced readers" I still try and take into account the subject of the book and who the books' intended audience is.
Liz at Tea Cozy linked to a great post from Alix Finn about parents who want to push "older" books on kids, just because they feel that if their child is in 4th grade and reading a middle school book, well then, they must be destined for greatness.
Another thing that I have run into a lot is when books are made into movies. I have 1st graders asking for different Harry Potter books or Narnia books and they tell me they can read them because "I saw the movie". I know this has been at the center of the debate on The Golden Compass movie, many christian and Catholic organizations are saying, the movie doesn't bring religion into it, but the books do, and if kids see the movie (which is pg-13) then they will want to read the books. Is The Golden Compass appropriate, content wise for a 2nd grader - well, I don't think so, I don't think many of them would "get-it". But then again, should a 2nd grader (who is usually about 7 or 8) be seeing a PG-13 movie?
I think that parents need to take an interest in what their child is reading, but I also think that they should try and steer them to books that would interest them, not necessarily challenge them. I was having a conversation about this very subject the other day with a parent at my school. She was complaining that some book series seem to get darker as they progress (she mentioned HP and Spiderwick Chronicles) and while she lets her 3rd grade daughter read the first 2 HP books, she said she is waiting to let her read the rest until next year or even 5th grade when she thought that she could understand the content better. - WOW, if only all parents thought like this!