Waterloo only penalizes grade 12 repeats but I wouldn't worry about upgrading grade 11 marks since they're only used for early acceptances. Instead, I would take G12 English or Chem in summer school and take a spare in grade 12 so you can focus on getting a higher mark in your other courses.

As far as I know Canadian universities don't look beyond grade 12 marks, heck they don't look beyond the required courses, i.e. if you take grade 12 history and apply to engineering, your history mark might as well not exist.

Don't worry too much about grade 11 marks - the more important thing is whether or not you've mastered the background needed to do well in the corresponding grade 12 courses. If you want to get an A in grade 12 chemistry, don't waste your time repeating grade 11 chemistry in summer school. Just read up on the topics you were weakest at and try to get a head start on grade 12 by reading the book in the summer.

In my case, it may be a bit biased because I finished all my grade 12 requirements for engineering except English when I was in grade 11 (I skipped 2 years of math, and 1 year of science). I finished calculus 12 in grade 10, and physics 12/chemistry 12 in grade 11. Damn counselors refused to let me skip ahead in English.

So when I was in grade 12, the only course I really needed to take was English 12 (everything else was just electives that I didn't need anyway), and when I reported my grade 12 marks to U of T they were all fully complete with high A's, except for English which was still in progress. That's why my grade 11 marks never mattered one bit.

I have some friends studying at Waterloo, and they told me that in their online applications they only posted their grade 12 marks, nothing more. And they didn't skip ahead like me, so their marks reported were in-progress.

You are bound to hear different information from different people. Exact admission policies are not really published by any university and people have just been guessing about it.

However, I believe that the university does have access to all your marks. Whether they use them as criteria is up to them.

However, I did read from somewhere (don't remember where anymore) that they do look at repeasted courses differently. It makes sense because if it's the second time you do the same course, you should do better.