This paper reviews the history of the continuum of services in intellectual disability programmes. The emergence of public school special education in the USA in the first two decades of the twentieth century is used as a case study of this history by focusing on events and personalities connected to the St Louis Public Schools. Using Annual Reports from the era along with the abundant publications and personal papers of J.E. Wallace Wallin, the author explores how the growing class of specialists in clinical psychology and psychometrics gained a foothold in the schools as educational gatekeepers for student placements along an increasingly elaborate "continuum of care". The paper interprets this quest for professional legitimacy as a three-sided conversation with Wallin (and his colleagues) in the middle between the medical officers of institutions for the feeble-minded on the one hand, and the educators of urban school systems on the other. Implications for the current discussions of inclusive approaches to education are discussed.