If you are under 19 years of age as of September 1 of the current year, and do not have your Alberta High School diploma, yes, you need to have the required pre-requisites in order to take a course. 

If you are a mature student, you are not required to have the pre-requisites in order to take a course. Courses build upon themselves so it will always be helpful to have the pre-requisite courses but it is not necessary. We encourage everyone to review the curriculum of the pre-requisite courses before beginning a new course. You can find the program of study for all high school courses here.