[dragonwriter]

> Previously, success on the SAT seemed to depend solely on how much money was spent on SAT prep.

Most likely, a correlation is not causation thing -- people for whom success on the SAT is most important are likely to spend more money on test prep, but also be best generally prepared. As ueqirat points out, the research that has been done on SAT test prep utility hasn't actually born out a real effect.

[mschulkind]

I know it's just one datapoint, and SAT II, not SAT, but I took the SAT II writing test around 2000 and got a 600. I then took a test prep course over a few weeks, took the test again, and got a 690, which is a pretty big difference I'd say. I can tell you the test prep course certainly didn't improve my writing at all...