<p>It was really rare in the past, because it was relatively rare for anyone to take both tests. Essentially there’s no reason to take both, especially if you already have the highest score possible on one. I don’t know of any college that won’t accept whichever one of them a student chooses. But increasingly kids seem to take both tests as a matter of course, so it’s probably going to be more common. It seems like about 350 kids/year get the top SAT score on a single test, and somewhat more the top ACT score. I would think at least 25-50% of the SAT group, and maybe a little less of the ACT group, ought to have a legitimate shot at the top score on the other test.</p>
<p>Now, I still don’t know why anyone with the top score on one test would waste a morning taking the other test, unless maybe they had taken the ACT first, and needed the SAT to get named a NMF based on their PSAT. Or really wanted a shot at being a Presidential Scholar.</p>