It misses the point: if you split the universe in two identical parallel universe, but then take the same individual and in one universe train them 2h per week, and in the other universe, train them 8h per week, do you really think, whatever the test is, the second one will not perform better?

This is the point of training: the more training you have access to, the better you do. If it was not the case, then the notion of school itself as a way of training people to be able to think by themselves will not have any sense.

And that is just training. Even with the same amount of class hour, kids who don't have to worry about take care of their siblings, of the house chores, or of even having access to decent relaxing conditions will get higher score even if they are in fact less smart.

There are studies that show how heritable intelligence is. Very.

It is quite common people say, that something is only a correlation and not causation. But if you can point to a common denominator, that has been shown multiple times, to have a massive effect, it's not likely to be just a coincidence. Genes are this common denominator. Society and habits (for example, protestants vs catholics) are another.

Things that consistently impact the whole population are not just a random process that picks: "You will be clever, ugly.", "You will be pretty, sporty, but will be dumb." It's always genes, society and habits.

Oh yes, I have kids in a prep school where half of the class goes to Eton, and the rest to Winchester, Harrow, Seven Oaks, Derby... Now, for the past few years, almost no parents want to send kids to Eton. They know how much are those kids discriminated against. It's better to send them to a school with lower profile.

Doesn’t this prove the reason for the existence of the disparity? The wealthy kid’s parents want tutors to supplement the education they get from their state school.

I understand an argument saying people will game this setup, but arguing that state school kids are not disadvantaged is indefensible, in my opinion

Your best argument is "we've done it for a long time, so it can't be wrong"?

Quite the contrary: there is a long history of "objective" tests being shown to be deeply flawed and biased towards certain factors (often cultural and class based), we explicitly know it isn't the case that test scores are purely about some innate intelligence characteristic: there is a reason the rich spend a lot of money to raise their children's scores.

My secondary school claimed to have the best results for Business Studies A-levels in the country. They achieved this by taking the pre-released case study, writing every possible question they could think of about the study, writing model answers, and telling the students to memorise them. The idea that these scores represent some innate intelligence of the student is obviously nonsense if you interact with the system at all.

I got six A's at A level, over 20 years ago.

Am i objectively smarter than every single other peer who only got 4 As?

(I, for one, am confident I know the answer to this question).

You could fairly say that China’s pre-Opium Wars obsession with testing and meritocracy based on said testing is what brought them into all that mess, I’m pretty sure that the Portuguese that had gotten all the way from their small country all the way to Southern China using some stingy boats were not clerks nor great (potential) test-takers, and yet it was those Portuguese seafarers that were to change the fate of most of Asia forever, not the test-taking Chinese.

We’ve done all sorts of dumb things for thousands of years.

It’s one metric of many. We know that paying for a tutor can change test scores. We know that a shitty home life can, too. They’re just harder to measure.