Only to some extent. I've tutored for the SAT and seen some improvement, but you can't get people to perfect scores. I got a perfect score with a bit of practice. Khan academy and the college board say your score can improve on average 115 pts with study, which is not nothing, but is still a long way from 1600 when the average score is ~1000.
So when someone says that people treat SAT scores as a proxy for an IQ test, they mean someone with a 1550 likely has a well-above average IQ, and a higher one than someone who got a 1250, who's still probably somewhat above average.
