I guess times have changed. When I took the SAT, I did zero prep work. Nobody else I knew did prep work, either.
Paul Graham recently posted SAT advice along the form of "when you finish the test and have more time, go back over the test and check for mistakes."
I was kinda astonished at this advice, isn't it obvious? A strategy I also employed was to do the easy problems first, so I don't miss a question that would have been easy. Apparently this has to be explained to people?
I suppose prep work would be fine for the students who didn't pay attention in class.