That’s just like with sports: anyone can learn how to train himself, and anyone can improve with training, but in the end, some people will end up faster, and some people will end up slower.
But of course, in addition to that, there is always also a genetic component, as in sports.
Everyone is well familiar with the downsides of standardized tests, but so far, nobody has proposed any alternative that better. Learning to the test is not great, but what’s the alternative? It’s not like anyone knows how to teach things that results in more actual knowledge and skills being attained despite lower test results.
And academic performance is measured how? With standardized tests?
So the question is, how much do these tests actually test skills in the subject matter and how much do they test "meta skills"?
It's not difficult to find first-hand accounts of this; go browse social media posts by teachers in mainland China if you're curious.
There are similar problems of "teaching to the test" in other contexts, too.
I'm not categorically opposed to standardized testing and I never said I was.
Feynman made such an observation while in Brazil:
https://enlightenedidiot.net/random/feynman-on-brazilian-edu...
My take away is the assessment method must force the student to actually apply understanding and application of the material, and not simply look y regurgitate it.
What you are describing, or the lack thereof, is how the majority of my public education in a Southern US state felt. Ironically, my county had the highest test scores in the state too. Then again, perhaps that isn't ironic after all...