Is it true that some Canadian universities only consider grades from senior year for admission?
No, it is not true for all Canadian universities. For example, in Ontario we use percentages for our marks and the admission average is about 88% for Queen’s university business program (the mark of your interim senior year when you apply and the final offer). However, Queen’s does not look at your application if you do not get over 80% in English or Maths (for the business program) in your junior year. So, what they expect iin your junior year is lower than what they’d expect in your senior year, but still you have to do well. Really depends on the university and program. Generally, more competitive universities or programs (another ex., McMaster Health Science) would take your junior marks into consideration.