<p>The SAT was never designed to measure changes in adolescence. The test is geared to 15 year olds in terms of content. Keep in mind that for a norm referenced test, the idea is that the test-taker should be able to score ~500. I'm not saying that every 15 year old ought to be able to score 800 - I'm saying that there is no reason to expect, based on test content, that in the absence of test prep and study that the test score will improve between administrations at age 15-18. </p>
<p>I mean, you can't even begin to draw conclusions about cognitive growth unless you first develop a test aimed at more advanced concepts.</p>