Thanks for sharing the link to that study. It's good that someone did a study relating to kids at the high end. On its face, the premise makes some sense but if you only look at the top percentiles like 98 and 99, the RIT norm charts actually show that these top performers increase their RIT scores during the school year (Fall to Spring) and stay about the same during the Summer (Spring to Fall). I only looked at the top two percentiles for 3rd through 8th grade but the Reading scores increased 5 to 12 points in math and between 3 to 8 points in reading during the school year but decreased 1 to increased 2 in math and mostly stayed the same or decreased 1 point in reading over the summer.
I suppose you can always make the argument that gifted kids do not score in these top percentiles so that these scorers in the top 2 percentiles are not the gifted kids but I find that hard to believe since MAP is so adaptive that it even yields huge score differences between the 95 percentile and the 98/99 percentiles whereas the 50th and 75th percentiles are tightly clustered. For example, for 6th grade Math, the 50th is 212 while the 75th is 222 whereas the 95th is 236 but 99th is 249.
