According to Henderson, the relatively new sport was not an immediate hit with his students. “Among blacks, basketball was at first considered a ‘sissy’ game, as was tennis in the rugged days of football,” he later wrote. In 1906, Henderson co-founded (along with Garnet Wilkinson of the M Street High School and W. A. Joiner of Howard University, as well as W. A. Decatur and Robert Mattingly of Armstrong Technical High School) the Inter-Scholastic Athletic Association of Middle Atlantic States, an amateur sports organization designed to encourage competition among intercollegiate and interscholastic athletes, in track and field as well as in basketball.