I think it's possible that your numbers of amount spent per pupil don't take into account the total benefit to that pupil towards their education. If Norway say also helps comparatively more with housing, food, and medicine, then that might also factor into the educational outcome of their pupils, especially if it means parents can spend more time helping their children.
Anecdotally the smallish town I grew up in had good public schools, and many of my teachers lived in nice homes nearby the schools they taught at. The HCOL city I currently live in has (supposedly) poor public schools and one of the issues I hear is that teachers can't afford to live anywhere near them and don't want to commute hours to work, so they have high turnover. If housing weren't so expensive the public schools here might be better while appearing to spend the same amount on education.
Anecdotally the smallish town I grew up in had good public schools, and many of my teachers lived in nice homes nearby the schools they taught at. The HCOL city I currently live in has (supposedly) poor public schools and one of the issues I hear is that teachers can't afford to live anywhere near them and don't want to commute hours to work, so they have high turnover. If housing weren't so expensive the public schools here might be better while appearing to spend the same amount on education.