 In high school, Arthur guided South Oak Cliff High School to back-to-back Texas 4A state titles in 2005 and 2006 and was the tournament's MVP both years.However, it was later determined that the school illegally changed player's grades to keep them eligible, and the titles have since been forfeited.Arthur went on to earn McDonald's All-American and third-team "Parade" All-American honors in 2006.