After graduating, Duncan played professional basketball for several years until 1991. In 1992, childhood friend and investment banker John W. Rogers, Jr., appointed Duncan Director of the Ariel Education Initiative, a program mentoring children at one of the city's worst-performing elementary schools and then assisting them as they proceeded further in the education system. After the school closed in 1996, Duncan and Rogers were instrumental in re-opening it as a charter school, Ariel Community Academy. In 1999, Duncan was appointed Deputy Chief of Staff for former Chicago Public Schools CEO Paul Vallas.