>Irrelevant. You and the grandparent are making an irrelevant point again and again. Why bring up diversity at all?
Because it's highly relevant when talking about an average value. The more heterogeneous a population is the less likely an average is to be useful.
>I already said there was going to be a "median" example... I was right about that, shocker. /s
Ranking by mean often isn't useful...shocker
>Except Canada and Switzerland and many other countries, right?
Sorry I meant large countries.
>If they are migrants, they're not representing the local education system now do they?
They're talking about long term migrants that represent about 40% of the population.
Look at Australia were 90% of 15 year olds are enrolled in school, vs. a country like Vietnam where 15 year olds routinely drop out and work.
How does that comparison make sense?
Some other examples.
In South Korea parents force their children to spend 4 or 5 hours with private tutors after school each day. South Korea performs very well on PISA league tables, but it probably says very little about the efficacy of the Korean school system vs any other country where parent don't routinely force their kids to pull double school shifts with private tutors.
Finland spends much more time teaching fractions than algebra to 15 year olds. The US outperforms them on algebra questions, but Finland outperforms on fraction questions. But PISA weighs fraction questions much higher than algebra questions.
In the US homeschooling is common. In Germany it's illegal. Home schoolers score much higher on the SAT and ACT, so in the US you're pulling 3 or 4% of the likely highest scoring students out of the pool--of course that's going to drastically affect the mean score.
We can't come up with tests that accurately compare abilities across cultures in the US. How can we possibly do it across 65 countries.
The answer is, you can't do it. Attempting to do it, failing, and publishing data that makes it look like you can is more harmful than just not publishing at all.
The critiques are numerous and come from very respected publications, organizations, and academics.
You can disagree with the critiques all you want, but you can't pretend the debate is over, and that there is some kind of settled science here.