He also briefly served as interim president of Virginia Tech after William Lavery stepped down in 1987 prior to James McComas' arrival in 1988. He was named president of Tech in late 1993 after McComas stepped down and served until January 2000. He taught at least one three-hour course each semester for the past 43 years.
This passage describes a person who served as interim president of Virginia Tech, then became permanent president after another president left.  He has been teaching for 43 years and teaches at least one three-hour course each semester.