Merit = money = race.
When you have more money for everything from childhood development to private schooling, tutoring, and test prep, you can essentially "buy" merit.
There's a reason SAT scores track with wealth.
Yeah, exactly.
So many factors go into it - childhood nutrition, parental pre-natal health and wellbeing, housing conditions (does a child have a quiet space to do homework?)...not to mention the way it all gets reinforced via culture - people, collectively, tend to make a virtue out of necessity, that is, they tend to learn to value whatever it is they have and devalue the things they don't, so if practical conditions make engaging in academic work particularly difficult the community as a whole will tend to devalue it.
And then on the other side of it, "merit" has a tendency to get defined as "whatever attributes the most privileged group tend to have". e.g. "high status" accents will be those that the high-status people have, and "good English" will be whatever form of the language the wealthier people tend to use.
It's why "meritocracy" is a concept that borders on meaningless. The very term was invented to describe something considered a bad thing in the first place. You can't have "equality of opportunity" unless you aim for "equality of outcome" - not least because one generation's outcomes are the subsequent generation's opportunities.
It was kind of darkly funny when during the pandemic the government decided to scrap exams and use an 'algorithm' to predict what exam results students would have gotten if exams had still gone ahead. And that algorithm, because it heavily weighted the school a child went to, effectively just assumed "wealthy white children will get better grades" and automatically accorded top grades to elite private school students by default, and failing grades to all working class students at 'bad' inner city schools.
A much quicker and easier way to achieve a pretty similar result to what the normal exam system gets anyway.