Phelps, the grandson of Seattle black pioneer John T. Gayton (1866-1954), began teaching in Bellevue in 1960 and became its first black principal in 1963. Along with being an educator, he also served locally as a news commentator on KOMO TV and Radio
From 1976 to 1988, he continued to rise through the hierarchy of education, becoming Interim Superintendent of Lake Washington School District 414 in 1976, president of Seattle Central Community College in 1980, and chancellor of Seattle Community College District in 1984.
In 1988, Phelps left King County to become chancellor of Los Angeles Community College District, the nation's largest community college system. In 1994, he was appointed W. K. Kellogg Regents Professor at the University of Texas at Austin.