This, to me, is a mystery. The US spends more per kid on public education than Canada does, yet our students perform better.
I have a few theories, but no way to prove them. First, in Canada, your taxes go to fund the education system all across the city... not to a specific small school district. So the quality of schools in Canada tends to be much more uniform across the country. Schools in poor neighbourhoods generally are as good as in wealthy ones. My three adult kids went to three different high schools in very wealthy, average, and poorer neighbourhoods respectively, yet the quality of education they received was about the same.
Second, there seems to be an irrational resentment of public school teachers in the USA. American teachers express much lower job satisfaction and much more pessimism than Canadian teachers.
Third, I think there is (and always has been) a strong strand of anti-intellectualism in the USA which devalues education. This is starting to show results.