I am looking for the title of a children's/young adult book that I read in elementary school, probably around 1977. It was the story of two Russian children during World War II, a girl and a boy. The girl dies near the end of the story, and the boy reads her diary. At one point, a parade of German POWs is passing, and the boy gives one of them his chocolate bar. Does anyone know what book this is?

Diary of Anne Frank I am certain

Yes. It's the diary of anne frank.