[JamesianP]

You can retake the test as many times as you want. Some schools average them, others will take the highest. The whole point of creating the test(s) in the first place were to deal with variability of GPA's between schools, so it's a bit useless to say "just adjust GPA's between schools instead".

In the US now we have federal school testing to try and normalize schools better. But before that many schools were graduate students that were illiterate (actually some still are, but I hope it's gotten better..). The US is 10x the population of Canada so image the difficulty for a liberal arts school in the northeast looking at a student from some rural 500-person school they've never heard of from the southwest.

[trinovantes]

Adjusting GPA between schools is one approach to deal with grade inflation between schools. SAT is just another approach with its own tradeoffs. I've simply listed why I prefer the former over the latter approach.

Canada's population is smaller but we also have many obscure rural schools. Non-prestigious universities don't have much data but they also don't have much choice in top applicants so it doesn't really matter. Over time, they can build up decently accurate profiles of high schools for majority of applicants.

[JamesianP]

They do a regression that includes both GPA and SAT. That is mathematically an adjustment of grades, where the adjustment is the SAT term. Then, as articles such as this one show, this correction correlates well with success at the university. So ultimately it becomes the same correction you want.

[trinovantes]

It would be interesting to see a study that compares SAT scores vs alumni performance to see which one has a better correlation with success to use for said adjustment

[sokoloff]

It's been many decades since I took the SAT (3x, at ages 11, 12, and 16), but I seem to recall that I had a choice of which schools to share my SAT results with, such that a school that only ever saw my age 16 SAT test couldn't possibly average in the other two scores.