Of course you’re correct that test prep can skew the results, but SAT scores are still one of the best measures available at scale, hence why they are so widely used despite the obvious flaws. Other than a DNA test for IQ, you can prep for any known test, whether it’s the SAT, the WPPSI, the WISC-IV, a Rorschach, or the New York Times crossword. As user wycs hinted at elsewhere, a polygenetic spit test for raw IQ potential - the Gattica scenario - is likely not as far off as we believe; when that hits, it’s a whole new world (from pre-conception.)
Again, SAT scores are an extremely poor measurement of intelligence, because at best they only apply to people who (1) speak American English with complete fluency, (2) have literacy in English, and (3) have been taught the syntax, symbols, and particular fields of math tested in math section. Beyond that, since the modern SAT includes a writing section, there is a large subjective component of the score that further reduces its usefulness as a measure of intelligence. The SAT I took had no essay, but even the old test would have done a poor job of measuring the intelligence of someone who did not receive a high school education.
The actual purpose of the SAT is to screen students for a minimum educational background needed to complete a four-year degree at an American college. It only applies to a typical American education, and only to certain specific aspects of that education (there is no section on music, art, history, etc.).
