What stands out for me is the very low coding score in comparison to the rest of his subtests, especially when you mentioned he takes a long time to do his work.
Same thoughts here. Especially your description of your ds knowing the answers but taking a long time to do his work - this is soooo very much like our ds in early elementary, and he also had a significantly lower coding score than his other subtest scores. The first time he was tested in early early elementary he was being tested for a gifted program and the psych who administered the IQ test said exactly what your psych said "he got every answer correct, just moved very slowly." The psych attributed that to him being young and not really understanding or caring that on this particular subtest speed mattered. My dh and I, when we saw how slow he was to produce written work and heard similar feedback from his teachers chalked it up to perfectionism because he seemed so obviously intellectually gifted when he talked. Each of us, parents, teachers, and that psych all missed a very big clue - that low coding score wasn't perfectionism, it was a sign of an LD (dyspraxia and dysgraphia for our ds). Not all low coding scores mean an LD - it could be anything from not caring to being tired of taking a test to worrying to who knows what - but fwiw, I'd think it's worth checking into a bit further with the types of follow-up assessments a neuropsych would offer - tests that assess executive function, fine motor skills and visual-motor processing. If you hadn't mentioned it taking your ds a long time to get his work done I might be more likely to guess the low coding score was just random.
At the very least, I don't think the FSIQ is a valid measure with the difference in processing speed you've noted, and you should be able to ask the psych who administered the test to calculate GAI for your ds. There are folks here who might be able to calculate it for you - I'm not one of them
FWIW, you have teachers and others who think your ds is gifted - don't change your expectations or lessen the challenge you feel he needs in school based on this one assessment. It's one data point, one measure of ability taken at one moment in time. It might be a good measure of his ability or it might be off - but in either case, ultimately it's achievement that matters in school
Have you had your ds evaluated for ADHD? Are there reasons you suspect it other than the slow response on work tasks at school? I think that would be worth following up on too, although I'd probably first try to rule out potential issues causing the low coding score.
polarbear
ps - even though you're in private school you could request testing through your school district, sighting the concern with slow output. Whether or not the school district would be willing to test depends on your district, but it might be one way to get further testing at no cost to understand what the low coding score means.
