I go to a mid-tier university (Toronto Metropolitan University) and the admissions average for CS was 97% last year.
The admissions process for universities in Ontario is a joke at this point. Imagine if students going to Harvard instead of SUNY Plattsburgh differed by 2 percentage points in their high school averages.
This means you must be absolutely perfect to have a shot of getting into a good school. In reality, teachers overlook mistakes and just give you the marks needed to get into top school if they think you deserve it. But because everyone does that, you also need to farm extracurriculars.
Maybe I'll write a blog post about this since it sounds like people are interested.