The SAT IS an IQ test, however much ETS denies it. The "A" in SAT used to stand for "aptitude", before aptitude became a dirty word.
Take yours truly.
HS average 88%. NYS Regents average 85%. HS GPA 2.99. Stanford Binet 4th grade = 144. (OK, yes, that = lazy).
SAT=1526 (old norm). MCAT = 788.
The only thing I ever did that correlated with my S-B IQ was the SAT (and the MCAT).
Thank you, ETS!
It would, however, be a lot simpler, and a lot more honest, to IQ test 11 year olds and track them for college or vocational school at that point.
I think they did that when I wuz a kid....