It is of course important to look at whether or not what you are measuring validly predicts what you are trying to predict. Despite much worry about SAT coaching courses, I get the very strong impression that the young people who score highest on the SAT are still, after all these decades, the young people who read widely for fun and who think about math problems for fun, just as they were in the 1970s when young people in my region of the United States were not coached for the SAT at all. The standardized conditions for administering the SAT have always included (in my lifetime) giving students registered for the test access to a complete previously administered test to serve as practice material. According to a psychometrician I know, precisely because the SAT allows everyone to practice in advance, it is an especially valid estimate of the test-taker's general ability to learn and to reason.

You can look up research about SAT correlations with general intelligence[1] and IQ test scores[2] and college grades[3] (what SAT scores are intended to predict) on Google Scholar and see for yourself what the empirical research says. No one-factor means of predicting college success is perfect (and if college admission officers were forced to use ONE factor to admit applicants to college, the factor they would be wise to choose to predict college grades is UNWEIGHTED high school grade average), but SAT scores (or ACT scores) are still used in the admission process of most colleges that are at all selective because they provide helpful information for comparing applicants who attended different high schools.

If you would like to put names of particular researchers into a Google Scholar search to find out what they have discovered about current use of SAT tests, I would suggest Nathan Kuncel or Paul Sackett, both of whom have studied quite a few detailed data sets about SAT-takers and what their scores predict.

AFTER EDIT: Terence Tao, in the interview kindly posted to open this thread, makes the important point that sometimes teachers entertain more than they actually teach. (I think a lot of commercial test-prep courses have this defect.) He said, "Sometimes making a class more enjoyable or entertaining is not the same as making it more educational. I remember once when I taught calculus, one of the sections was quadric surfaces, like ellipsoids, paraboloids and so forth. So there’s this thing called a hyperbolic paraboloid, and I wanted to demonstrate this. It turns out that a Pringle has the shape of a hyperbolic paraboloid. So I brought in a pack of Pringles to class and said, 'this is a hyperbolic paraboloid, this is what it looks like.' I ate the Pringle as I was writing equations on the board. Well many years later, I ran into someone on the street who said, 'Oh, I know you. I took one of your classes. I forget what it was, but there was a Pringle.' So I thought, 'you didn’t remember any of the math, but you remember the Pringle.' So it didn’t really work." Following up on that in the context of this subthread, I think a lot of students know who Joe Bloggs[4] is without being able to reason successfully to find the right answer choice on the harder SAT questions.

[1] http://scholar.google.com/scholar?hl=en&q=SAT+general+intell...

[2] http://scholar.google.com/scholar?q=SAT+IQ+test

[3] http://scholar.google.com/scholar?q=SAT+college+grades

[4] http://books.google.com/books?id=K4SteOicBAQC&pg=PA23&lpg=PA...