In my day, all high school students in my State in Australia took the same exams to determine eligibility for entrance into tertiary institution courses. These

In my day, all high school students in my State in Australia took the same exams to determine eligibility for entrance into tertiary institution courses. These scores were the only thing known about the student and the only thing considered. This was regardless of whether you went to an expensive private school, public school or any other factor. Why is merit alone not the criteria everywhere? Is membership of some group as criteria to entry not discriminatory to others?