This paper concentrates on a seminal figure in the history of Canadian education who has never previously been the subject of historical examination: Duncan McArthur. As Deputy Minister, then Minister of Education, in Ontario between 1934 and 1942, he guided the province's public schools during a period of dramatic reorganisation within a context transformed throughout the interwar years by modernity, economic instability, urbanisation and industrialisation. Under McArthur's leadership, revised programmes of study formally introduced the rhetoric of progressive education into Canada's most populous public school system. This rhetoric wove together three distinct themes--meliorism, efficiency and child study--articulating a progressivist educational vision for Ontario's teachers and students.