McClelland received his bachelors, masters and Ph.D. all from the University of Pennsylvania in 1903, 1912 and 1916 respectively. He began his teaching career as an English instructor at City College of New York in 1903. In 1911 McClelland became an instructor in English at Penn and then in 1917 he became an assistant professor of English at the University of Pennsylvania. In 1924 he was made a full professor of English, a position he held until he was given emeritus status in 1950.
At the same time as he held his academic positins McClelland also held administrative positions. He worked as assistant director of undergraduate admissions from 1915−1921. From 1921 to 1925 he was Penn's director of undergraduate admissions. He then served as vice provost from 1925−1928. From 1928 until 1931 he was vice provost in charge of undergraduate schools. He then became vice president in charge of undergraduate schools, a position he held until his appointment as provost in 1939. After he stepped down as president in 1948 McClelland served as a trustee of Penn until his death in 1955.
The Chief administrator prior to 1930 was the provost. The provost had oversight of the College faculty, except for law and medicine, until the administration of William Pepper.In several steps, over the course of Provost Pepper's tenure, all faculties began to report to the Provost.
Penniman continued as provost after 1930, in a diminished role after reorganization.