Wow Null, for me it was easy to get the Medic MOS and i'm a highschool dropout technically (homeschooled and parents didnt print out records before the hard drive that contained them got wiped out...)
I just had to score high enough on the asvab test (armed service vocational apptitude battery, basically an IQ test in case y'all go by a different test in Canada) and have a GED. They took me, no questions asked.
Canada seems pretty strict about what you can and can not do in the military. As for us, all they ask is that you score high enough on the test and they could have you working on nuclear crap just out of highschool.