A Full Scale I.Q. (FSIQ) of 158-160 is different than an a General Ability Index (GAI) of 158-160.
According to Pearson's free online
pdf document, "The What, When, and How of the Wechsler General Ability Index":
• The GAI provides an estimate of general intellectual ability, with reduced emphasis on working memory and processing speed relative to the FSIQ.
• Theoretically, the GAI represents an individual’s overall cognitive ability, if working memory and processing speed abilities were similar to verbal and non-verbal abilities.
emphasis addedA large discrepancy in scores may indicate a learning disability. A gifted child with a learning disability may be called twice exceptional (2e). If this may apply to your child you may benefit by becoming familiar with
wrightslaw and the book
From Emotions to Advocacy.
What research indicates about identification procedures is that you should match the identification procedures to the intervention programs. That is, if the program is going to require a kid to do stuff that relies on WM and PS, don't use GAI for identification, because you're going to end up getting kids in the program who then can't handle the work, and you're going to exclude kids who should be in the program.