The War of Jenkins' Ear by Michael Morpurgo

Wonderful school story. A synopsis is provided by Carol on her website: "It all takes place at Redlands school, a British prepatory school - not a bad place as such schools go although Toby hates it. Toby Jenkins is a second year student there and though he dreads the moment when the new term starts, he's made a kind of grim adjustment to the mindless rules and conformity demanded here. It's Christopher, the new boy, who upsets it all. He seems completely unafraid of teachers or bullies and he tells Toby and Swann that he is Jesus Christ reborn. Neither the reader nor either of the boys is ever sure whether that's delusion or reality."