Sybil Marshall's early career was as a primary school teacher in a one-room school in the Fenland of Cambridgeshire. At age 48, after her small school was closed, she went to Cambridge University to read English and then was appointed as lecturer in primary education at Sheffield University from 1962 to 1967. She taught at Sussex University for about another 10 years. Her writings on educational methods became highly influential in Britain. Marshall also published her memoirs of life in the Fenland, which were called "a classic of the rural past," and a series of novels. From 1965, she served as an educational adviser to Granada Television.