In almost all countries students can enter medical, dental, pharmacy, law schools after high school education but not in USA & Canada. Probably the reason to this is to avoid most of the bright students prefer to enter directly to these branches just due to their relatively higher average incomes. So let them see other branches also and if they can excel let them go to their path rather than medical, dental, pharmacy, law schools since every branch needs best students. It is relatively difficult to enter medical, dental, pharmacy, law schools with very competetive entrance examinations such as MCAT, DCAT, LCAT and other credentials whereas most of them fail due to lack of places in these schools. Other than these, after admission to these schools courseworks also require much more effort since they are directly involved with the well being of each individual person by the service these professionals. Since I entered in most popular medical school in my country after high school I rather prefer to enter medicine after secondary school.