Markus Zusak's The Book Thief (Knopf, 2006) - I just loved this book. It was so gentle and so strong. A story of a girl during the Nazi times. Here's a sample of his poetic-like writing: "In the darkness of my dark-beating heart, I know. He'd have loved it all right. You see? Even death has a heart." And even the German children had hearts. As a child of Germans, I judged my own parents as guilty for participating in the war. Children can be harsh judges.
And one more book I'd like to recommend is Joan M. Wolf's book, Someone Named Eva (Clarion Books, 2007) It's about a place that no longer exists. A place called Lidice, Czechoslovakia. A powerful story about the Lebensborn program. Plus, it's a debut novel.
The survivors of last century's wars are old, feeble people now. It's easy to forget that they were children and involved in some of history's most horrible events. These books are about connecting the past to the present. Mid grade is that stage where they're curious about the world. Later, in their teens, they often become more involved with their own emotional turmoil as puberty takes over.
So historical fiction for mid grade is a powerful way to teach history.