Here, on HN and on Scott's post, there's an implicit equating of "meritocracy" with "test score."
Do people here really think test score and ability — to say the least of merit per se — are equivalent?
Go find a scatterplot of some data correlated 0.80 (e.g., https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3576830/). That's a very generous estimate of how correlated that test score will be with actual ability, whatever that means. The correlation probably is lower, like 0.50-0.70. Look at the y axis. Now cut it and take the upper fraction of your choice. See how wide a range of the x axis is represented?
That's the problem.
The reason why test scores are a problem is because when you select on an imperfect indicator, at some level you are randomly selecting with regard to actual ability, which is even further removed from merit. Throw in any kind of bias of any sort associated with anything, and the problem gets worse.
The truth is, it was already a lottery before. It was just a lottery that everyone pretended wasn't a lottery, and that's the problem people have with it.
The problem with meritocracy isn't the idea of selecting people based on merit, it's the idea that test scores or other such quantitative metrics are equivalent to merit.
The analogy with sports is fundamentally flawed because, among other things, the metrics are the thing of interest in sports. If you are interested in who can swim 50m the fastest, then your speed on the 50m swim is the metric of interest. In school, though, presumably you're not interested in test score, you're interested in someone's ability to solve problems, or create things, or be productive, or whatever. And we're not talking about sport, we're talking about gateways into careers in general. If we are selecting into schools to maximize ability to achieve high test scores on standardized tests per se, then at least be frank and honest about that, and accept that what you are arguing is that the school is an institution whose purpose is to achieve high standardized test scores, and nothing more. But if you want to argue that the school should produce people who are solving problems, innovating, and so forth, then you need to be honest about selection based on test scores, because the scores aren't what they intend to measure.
Scott laments the loss of the ability of some kid to work their way into the school based on some test score. But shouldn't he be screaming about a system that doesn't provide resources to kids where they're at? That assumes the kid's ability is equivalent to their score on some entrance exam? What about those problems?
I agree that throwing out test score and relying on GPA per se is a problem; relying on GPA alone is just as much of a problem as relying on test score alone. You could, for example, have a lottery for everyone whose score is above some generous threshold, or for everyone whose GPA or score is above some threshold. But staying with the system as it is seems at worst like turning a blind eye to systemic injustice, and at best like missing the forest for the trees.