A friend of mine had a low average in grade 12 and wanted to do social sciences...he called mac and asked if they can wait for him after he takes a summer school course to boost his average and they said that they accept people who do that if they are applying to social sciences and humanities.
That was 3 years ago, so I am not sure if the system has changed.
What I am trying to say is, they might be still accepting people now.
Good luck