<P> 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 . </P> <P> 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 . </P>

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