His cognitive results are certainly highly variable, with the WISC-IV results apparently lining up with his language-related achievement, and his 5th grade CogAT paralleling his math-related achievement. (I'm not so concerned with the grade 3 CogATs, which are within striking distance of the WISC-IV.) One question that comes to mind is whether any remediation for the ADHD and dysgraphia was instituted after the 4th grade eval. Dysgraphia would be unlikely to affect the majority of the WISC results, with the exception of 1/3 of the PRI, and 1/2 to all of the PSI. It obviously was felt to have an impact on the writing portions of the WIAT, or there would have been no diagnosis. ADHD not uncommonly depresses scores on all kinds of tests, cognitive assessments included, and sometimes in apparently inconsistent ways. If the ADHD was pulling the WISC-IV scores down, but was better managed in fifth grade, it is conceivable that his scores could have gone up on that CogAT, to something more closely approximating his "true" ability. It may also be that he was more engaged for the CogAT, and not so much for the WISC-IV. If he's always enjoyed math, that section of the WIAT-III may have perked him up enough to show off some of his paces. It's not always obvious how much inattention is affecting children with ADHD-primarily inattentive, since they're not as disruptive in classrooms.
In any case, I prefer to base placement decisions on actual performance, rather than purely on cognitive assessment (though of course one takes it into account). If he is successful with coursework at a certain level and pace now, that would be the best predictor of success with an analogous level and pace at the high school level, regardless of formal test scores.
