The SAT was designed to produce a more egalitarian, less elitist American college student, yet few are ever really happy with it. I tend to view it roughly as an IQ test, but one which conflates the upper end to eliminate the upper outliers (it's not fair to the others to be too good).
From Steve Sailer's Asians, aptitude, and achievement: a positive sum reform proposal (h/t AVI):
...once the Ivy Leagues started trying to find the most promising non-upper class kids from the rest of the country, they needed something more objective about individuals than just grades. Another issue is that high school grades have certain inherent shortcomings. The future Nobelist in physics might not care about his social studies class and thus wind up with a lower overall GPA than the well-adjusted grind. Plus, grades have a ceiling. Even an A+ in physics doesn't really tell you that much. Moreover, lots of future successes are alienated in high school. Some people who get all As in high school might not have the upside to continue to do so in college. Incentives toward grade inflation at the high school are built in. And so forth ...