When he was eight, King's parents brought him to basketball camps run by Louisiana Tech and the Dallas Mavericks. Organizers of those camps realized quickly that King played at a much higher level than others in his age group, and recommended that he instead play in the Amateur Athletic Union (AAU). By the time he was in eighth grade, King was playing alongside high-school juniors and seniors. When given the opportunity to play in place of a guard who had fouled out, King sank three three-pointers in a row, helping his team to win the game. As a 14-year-old, he played on an AAU team for 17-year-olds, scoring six three-pointers in one game in the state playoffs before helping the team to win a national championship.