Before the SAT, colleges gave their own achievement tests to see whether you were prepared.
In 1926, the SAT was intended to be a "progressive", democratizing influence by testing your "aptitude" instead of your mastery of Latin, Greek, French, chemistry and trigonometry. At the time, the elite prep schools did the best job preparing kids for the elite colleges' requirements.
Charles Murray on educational testing, college admissions, class and genes. He suggests dumping the SAT, but keeping the Achievement Tests. His discussion makes sense to me: a college ought to be able to state what they expect in terms of preparation.
On the same subject, Ivy Leaguers take untimed SATs. ADD and dyslexia, ya know?