Here in the UK (small country, we talk funny and it rains a lot) the big controversy in Children's Fiction right now is the labelling issue. A couple of well-known writers are pushing hard to get all children's books given an age-appropriate tag, so that the 'right' readers will read them and they will be placed on the 'right' shelves in bookshops.
Slippery road towards censorship? Or About time? You probably have your own views. This is my twopennyworth (umm ...don't know what that would be in cents,sorry). I write crime fiction, based around a 15 year old heroine. The point is, I get read by anyone from 10 to 64. Maybe older. My books are found in the general children's stories section, also in the teenage area. If you try to label me as 'this' or 'that' you limit my shelf area, and maybe deny me sales. Or readers.
I also give author talks to secondary school pupils, and I always ask them what they're currently reading. The responses vary from Harry Potter to hardcore adult crime fiction. Some even express a love of the classics: Dickens,Jane Austen. Kids are at different levels in their reading. Some like short, easy books. Another child in the same class may be hitting the 'adult' shelves. You can't tell them what to read: they are all at different levels. They need to discover what they like for themselves. Firstly from the cover, which is a very good indication of the content, then from the blurb at the back, then from dipping into the book and having a taste of the story.
I don't have a particular age group in mind when I write. I just write what excites me, hopefully, what excites my readers too, and I don't want some arbitrary person deciding what age group my stories are 'suitable' for. Please, let the kids decide for themselves! So, that's my opinion. What's yours?