Have been following this thread with interest, not so much because of the Holocaust debate, but more because of the comments made regarding children reading books with a content aimed beyond their years.
As a children's bookseller, I have noticed a real rush amongst parents to move their 9, 10 and 11 year old children into the teen section because 'they're a really good reader.' Often, the books in the teen section are no more difficult to read than some of those in the 9-12 section; it's just that their content is aimed at older readers and, therefore, may contain reference to topics unsuited to younger children.
I run a series of inschool reading groups aimed at able readers. I have noticed two interesting facts arising from these groups. Firstly, a lot of children do not like Michael Morpurgo and, secondly, yes, a lot of Year 5's and 6's are reading books written by authors such as Charlie Higson (The Enemy) and Robert Muchamore, which are definitely aimed at older readers. I think this is because the books are written to appeal to a more reluctant older reader, which makes them ideal for a fluent younger reader 'reading wise' but not so content wise IYSWIM.
However, I would not give my Year 5/6 reading groups 'The Enemy' or Robert Muchamore. I would not expect to find these books in a primary school library, nor would I expect a primary school teacher to read them as a class book. It is ultimately for the parents to decide whether they are happy for their younger child to read books aimed at an older readership.
In my shop, TBITSP is classified as a teen book. The publisher of the book states that it is not a book for younger children, even though the book is about a 9 year old boy.
There are so many really good books with a content appropriate to a Year 5/Year 6 child. Save the teen books for when they're ready