Because of Canada's immigration policy, most of the immigrants are highly educated, they wouldn't be an immigrant if they didn't finish high school. Refugees is everyone else who couldn't immigrate and had to go the other route. So you might have a Sudanese immigrants who are highly educated and Sudanese refugees who are more likely to be illiterate (a bit generalizing but still).

This is very different from US where you have a green card lottery and your typical immigrant is just an average population because everyone has the same chance of winning lottery, it doesn't matter if you are a farmer or aircraft engineer.