My dd10's verbal part of the her CogAT was hugely lower than her verbal index on the WISC. She's taken the WISC twice and both times had a VCI (verbal index) at or above the 99th percentile. I can't recall her exact verbal CogAT score but it was one of her lower scores with Nonverbal being, by far, her highest. She, too, had a less than ideal testing circumstance on the CogAT and I just don't think that it is a good test for her anyway as she's a very out of the box thinker.
My first step would be to find out whether your school will accept outside testing and what score on it they'd need in order to id him as gifted.
