Ours uses above level CogAT. So DD took the CogAT 6A (third grade) a couple months after her 7th birthday. Her verbal score was 130, or 97th percentile for her age. But 95th percentile for the grade score. Since she was accelerated, and technically should have still been in first grade, she would have been one of the youngest kids taking that level of test. I'm assuming they are comparing her to other second graders who took the test, not third graders. On the report it says she is in Grade 2 so obviously someone entered that in the system. It also says Norms: Midyear 2005. Not sure what that means. She took the test Jan. 2013.
Not sure if this helps to answer your question. In terms of which score they use, they only care about the composite score, or standard score (whatever it's called), so they have cut-offs like 132 or 139. I think those are based on the child's age, not grade.