The Whipping Boy by Sid Fleischman
It is the Middle Ages and Jemmy is Prince Brat’s whipping boy – this means when the prince misbehaves, Jemmy takes his punishment for him. The two boys can’t stand each other, but when the spoiled prince runs away, Jemmy is forced to go along. Then they are kidnapped and Jemmy is mistaken for the prince while the prince is thought to be a commoner. Colorful and humorous characters add to the fun adventures the boys have while out of the castle. Through their experiences, the prince learns about friendship and becomes a better and more thoughtful person in the end. Winner of the Newbery Medal.