The government of Ontario announced in 1984 that it would begin to fund Catholic high schools in 1985. Prior to this announcement, Ontario had operated since the 1800s under a system that provided for the public funding of a dual system of Protestant and Catholic public elementary schools and a single system of nondenominational secondary schools. Since the majority of Ontario's residents were non-Catholic, this arrangement developed into a system of essentially nondenominational public elementary and secondary schools supplemented by alternative public, Catholic elementary schools and a scattering of private schools of various types. This system of alternatives is now being extended into secondary education. The change raises a number of legal and constitutional questions, however. This paper reviews the historical factors behind the creation and development of Ontario's public school system, examines the constitutional issues raised in relation to Canada's Constitution Act of 1867 and the recently adopted Canadian Charter of Rights and Freedoms, presents the findings of the Commission on Private Schools in Ontario (created when the decision to fund Catholic high schools was announced), discusses recent court decisions relevant to the issues, and suggests possible ways in which the debate may be resolved. Twenty-six footnotes are appended. (PGD)