My DD had a similarly bad math CogAT score (it wasn't much over 100) but the compuerized math acheivement testing the school does is over the 99th percentile, or several grade levels ahead. So obviously she is able to understand math concepts. Like your DS, she only answered about half the questions. The ones she did answer were very accurate. A kid has to finish the test in order to get a high score. She is slow with ADHD and processing speed issues, and that has nothing to do with actual math reasoning ability. Tell them that section shouldn't have been scored since he left half of it blank. It's not normal to have that big of a gap.
