Glynn Russell Turman (born January 31, 1946) is an American stage, television, and film actor as well as a writer, director, and producer. He is perhaps best known for his roles as high school student Leroy "Preach" Jackson in the 1975 coming-of-age film Cooley High, math professor and retired Army colonel Bradford Taylor on the NBC sitcom A Different World, and fictional Baltimore mayor Clarence Royce on the HBO drama series The Wire. From Wikipedia, the free encyclopedia.