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.