Clayton was called into the England under-20 squad for a friendly against Italy in March 2009 to replace Tom Cleverley, who withdrew from the original selection. England won 2–0, and Clayton made his international debut as a second-half substitute for Josh Walker. He was a member of England's squad for the 2009 U20 World Cup, where he wore the number 4 shirt. He started two of England's three matches as they were eliminated at the group stage.