 In this position, he followed Octavius V. Catto, who was shot in a riot.From January 1 to July 1, 1873, he was principal of the Sumner High School, a Preparatory School for Colored Children in Washington, D.C.. Greener accepted the professorship of mental and moral philosophy at the University of South Carolina in October 1873, where he was the university's first African-American faculty member He also served as a librarian there helping to "reorganize and catalog the library's holdings which were in disarray after the Civil War" and wrote a monograph on the rare books of the library.His responsibilities included assisting in the departments of Latin and Greek and teaching classes in International Law and the Constitution of the United States.