So, it sounds like there was some consistency btwn the OLSAT and CogAT in that he was in the MG or slightly below range on the non-verbal part of each and not in the gifted range on the other parts. Since the CogAT composite score came out in the 5th stanine, though, I'm having to imagine that his verbal and/or quantitative parts came out below average to bring down the non-verbal part.
Given what else you say, I do wonder if having to read it himself might have slowed him down and impacted his scoring. The non-verbal part doesn't require as much reading so that would make sense that it would be his highest area if he struggles more with quick reading.
If you have the ability to do so, I'd see if you can get a more individualized eval done: IQ, achievement, and maybe a look at dyslexia.
