When Mark Twain wrote The Prince and the Pauper back in the 1880s it was a highly original concept. But many stories with a similar theme have been told since then.
You could say Faith, Hope, and Ivy June by Phyllis Reynolds Naylor is based on the same idea, but it's very original.
In this story wealthy Catherine and poor Ivy June don't exactly trade places. Instead each one spends two weeks living with the other and attending her school as part of a student exchange program. And the girls must cope with differences like Catherine sharing a bathroom with her sister and Ivy June using a chamber pot and an outhouse. There are also some conflicts with other kids in each place.
But that's just the beginning of the story. I don't want to give away the plot, but the events that happen next are far more dramatic than the conflict between two economic levels. In fact the girls must deal with some real disasters.
As in her other books, Naylor does a great job of making the reader care about the characters and really feel involved in the story.
In my opinion this is a terrific book.