1. Max'ing out on the scaled score with all items correct is another example of hitting the test ceiling, and shows yet again that this test doesn't have sufficient range to distinguish learners at or above your child's level.
2. The hypothetical maximum scaled score is, I believe, 160, but, as noted in 1., not every age bracket allows for anyone to reach the max score, due to the insufficient ceiling of the test.
3. The difference between the lowest and highest scores you've listed, let alone the very minor one between math and language arts, would not be considered particularly significant.
These remain, of course, extremely strong scores all around. My observation above also holds, which is that his individually-administered assessments are much more likely both to accurately reflect his ability, and to provide detailed information about his learning, than the CogAT is.
