Nagpuon na magtrabaho si David kan 1966 bilang Teaching Assistant sa Department of Sociology kan Unibersidad kan Pilipinas Diliman. Nagin syang Assistant Professor puon 1970 sagkod 1975. Kan 1986, itinalaga sya sa Departament of Social Welfare and Development. Puon kan 1975, nagin propesor si David nin community development sa College of Social Work and Community Development kan Unibersidad.