Standard Score (NAI) 122 is normally 93rd %ile, so something is slightly odd about his scores. And 95th %ile is only 2 points higher, at 124. Perhaps they're using district/local norms.
That being said, 122 (equivalent to scaled score 14) is not statistically significantly different from 16 (equivalent to SS 130-134)on Matrix Reasoning, which is essentially the same task. Nor is it much different from the WISC-IV PRI of 131 (given that these are comparisons across different tests, not within test). I would say that the apparent huge discrepancy between the WISC-IV GAI and the NNAT2 NAI would suggest investigating the 2e angle (both PSI/WMI and emotional) more so than questioning the validity of this NNAT2.
If you wanted to pursue a GATE appeal, you could argue that a two point SS difference is well within the SEM/confidence interval for the instrument. I don't have this test, so I can't look up the exact numbers, but I don't know of any cognitive instrument that has a SEM less than 2, so I think it likely that this would be true. They should have this info in their manuals for the NNAT2.
The value of appealing would depend largely on whether you think the actual GATE program would suit your child, or if GATE identification would have any other function.
