From those early years through the 1950s, Henderson also played and coached basketball, as well as refereed football and baseball contests and occasionally sparred in the boxing ring. He helped organize the first all-black amateur athletic association, the Interscholastic Athletic Association (1906), the Washington, D.C. Public School Athletic League (1906) and the Eastern Board of Officials (1905) (a training center that, for decades was the go-to pool for highly qualified African American referees). Henderson taught and influenced perhaps hundreds of thousands of Washington area schoolchildren in basketball, including Duke Ellington and Charles Drew.