At age nine, Williamson began waking up every morning at 5 a.m. to go train.[2] He competed in youth leagues with his mother Sharonda Sampson coaching and played for the Sumter Falcons on the Amateur Athletic Union (AAU) circuit, facing opponents four years older than him.[3] Williamson later began working with his stepfather, former college basketball player Lee Anderson, to improve his skills as a point guard.[3] He joined the basketball team at Johnakin Middle School in Marion, South Carolina, where he was again coached by his mother and averaged 20 points per game.