Computer science at Waterloo is extremely competitive. The acceptance rate is about 10%. The acceptance is holistic as well, so your extracurriculars will be important.
@bouders when we were at a tour this summer, the acceptance figures given out for the most recent class were lower than that. Came out to something like 5-6%. The acceptance might be "holistic’ for a Canadian school, but they are far more grade and test based than most American schools.
Thanks for the current info @57special. My info was from the 2017 class. Waterloo is more grade based, but students won’t get in without EC’s. Students complete an AIF (additional information form) which is scored and the result is added to the students’ grades. Students with the highest overall score are admitted, but they must also meet a minimum score on their grades. My info (which is outdated), is that the overall score necessary is >100%.