The Ontario Academic Credit or OAC (French: Cours préuniversitaire de l'Ontario or CPO) was a fifth year of secondary school education that previously existed in the province of Ontario, Canada, designed for students preparing for post-secondary education. The OAC curriculum was codified by the Ontario Ministry of Education in Ontario Schools: Intermediate and Senior (OS:IS) and its revisions. The Ontario education system had five years of secondary education, known as Grade 13 from 1921 to 1988; grade 13 was replaced by OAC for students starting high school (grade 9) in 1984. OAC continued to act as a fifth year of secondary education until it was phased out in 2003.
The fifth year in the Ontario secondary school system had existed in Ontario for 82 years, from 1921 to 2003, first as Grade 13, and then as the Ontario Academic Credit. The first attempt to reform the education system in Ontario was initiated in 1945, with the Royal Commission on Education, which proposed a three-tiered education system with six years of elementary education, followed by four years of secondary education, and culminating in three years of junior colleges. However, the commission's report was shelved after five years, in part due its potential to re-open the politically sensitive issue of separate school funding and in part due to the Minister of Education's prior interference in curriculum redesign a year earlier.
The threat to the fifth year of secondary school education in Ontario grew significantly during the 1960s, with growing opposition to the grade 13 departmental examinations from parents. This led to the establishment of the Grade 13 Study Committee in 1964 by Minister of Education Bill Davis, which recommended the elimination of both the departmental examinations, and grade 13. A subsequent recommendation in 1968, in the Hall-Dennis Report, also called for the elimination of grade 13. In spite of these recommendations, however, grade 13 was maintained by the Ontario government.
A significant opposition amongst parents, businesses and universities regarding the education reforms had surfaced by the 1970s, in which they believed there was a decline in academic standards, a lack of focus in the curriculum, and lax discipline in schools. Combined with financially pressured school boards beginning to call for the abolition of grade 13 as a means of financial restraint, this resulted in the government reevaluating its secondary education system. The resulting document was the Ontario Schools: Intermediate and Senior (OS:IS), which had called for the formal elimination of grade 13, without formally eliminating the fifth year of secondary education. Acting upon the recommendations of the document, Ontario formally eliminated grade 13 in 1984, and introduced the Ontario Academic Credit system. The new system allowed for students to graduate secondary schools in four years, while also maintaining the fifth year, known as OAC, which had courses catering for students planning to proceed with post-secondary education. Despite the fact that students were able to graduate the secondary school system in four years, a fifth year of secondary education continued to persist in Ontario, with fewer than 15 percent of students exercising the option to graduate in four years, with reports that between 20 percent and 25 percent of students choose to repeat one or more OAC years.