Duncan started one of the first community early intervention programs in North Carolina which encompassed a rural, five-county area. He served as local and regional coordinator for services for all children and adults with developmental disabilities, and then was employed as the chief of Community Support Services for the NC Division of Mental Health and Developmental Disabilities. For the next twenty-five years, he directed the NC Early Intervention Program with responsibilities in such areas as system planning and evaluation, policy development, resource development, budget management, professional development, and family involvement. During this time, he served as President of the National Infant and Toddler Coordinators’ Association.
Following his retirement, he helped plan and design an interagency integrated early childhood data system which was funded through North Carolina’s Race to the Top Early Learning Challenge Grant and served as a Project Manager with the NC Council on Developmental Disabilities. He has also taught early childhood special education as an Adjunct Professor at the University of North Carolina at Greensboro. He has served on a number of Boards including the Frank Porter Graham Child Development Institute Executive Leadership Board, the North Carolina Family Support Network, and Community Partnerships, a community organization providing early intervention services. Other volunteer activities include working at the Neo-natal Critical Care Center at UNC Memorial Hospital.