Here's my input - it may come across as random and scattered - hope it helps a bit!
I think if the low dip in coding speed was related to a true LD (visual challenge or fine motor skill) you'd also see a low dip in the academic fluency score, because those tests require handwriting and are timed. "Academic Fluency" Is a combined score, made up (if I remember correctly) of writing fluency, math fluency and reading fluency. If there was scatter in the fluency subtest scores that might mean something, but I"m guessing your ds is solid across the subtests.
I have heard repeatedly over the years that low processing speed (coding) shows up in the WISC profile for kids with ADHD. That doesn't mean your ds has ADHD, but you've had feedback from school that he has behaviors that sound similar to what you'd see in a child with ADHD and the psych also commented that it's a possibility. I *wouldn't* want to wait 2 years to figure out if your ds has ADHD or not, but it also probably isn't something you are going to figure out right away. I would ask your pediatrician for a referral for an ADHD evaluation - the type of evaluation where the dr takes a developmental history and has parents *and* teachers fill out behavioral questionnaires. Our ds was diagnosed with ADHD (inattentive type) in 2nd grade, but he is also EG and 2e. What clarified things for us was the ADHD-specific evaluation.
I wouldn't totally ignore the possibility of an LD either - as I said, I don't think you have signs of one in the scores but he does have a very low coding score relative to his other scores. If you notice he's struggling at all with handwriting or keeping up with timed assignments, then I think it would be worth investigating the low coding score further. FWIW, the behaviors that our ds had that his teachers attributed to ADHD in 2nd grade were actually behaviors due to his undiagnosed LD - he doesn't have ADHD.
Last thought - I was a little surprised your psych didn't give you scores for VIQ and PRI on the WISC. They do have scatter, and I've read that the degree of scatter you've seen is enough to have questions about the accuracy of averaging them together, but I've also never seen a report with that (smallish) degree of scatter not scored for VCI and PRI (but please know I'm not a psych, just the mom of two 2e kiddos!). I am *not* surprised they didn't calculate the FSIQ given the relatively low processing speed score, but I think the GAI (given it's calculated correctly) is a good estimate as long as the subtest scores for VIQ and PRI are roughly accurate.
Did the psych make any notes about attention or being distracted during the WISC?
Last thought on the coding speed - our ds had a very low coding score on his first WISC. At the time the psych felt it was due to his age (6) and not really "getting it" that it was important to move quickly on a timed test, and possibly being a bit of a perfectionist and she expected it would go up in a few years when he retested. She said these were very typical things for a 6 year old - so I am restating it only to let you know she felt they were very typical and wasn't surprised by a dip in processing speed when testing young children.
polarbear
Thanks polarbear - a lot of good information in your reply.
Here are his subtests on WJ-III.
Reading fluency 128
Math fluency 112
Writing fluency 128
But he got a 162(!) in calculation...I've seen him write out all the multiplication tables quickly - he draws fast and his handwriting is great (they teach cursive in Montessori beginning in K)
I think what you said about his age makes sense. I don't think he has had to do much timed work in Montessori and maybe didn't realize he was supposed to move quickly.
Just today, DS told me that he didn't do two in-class assignments he was supposed to do because he was doing other things and ran out of time. *sigh* At least the school knows that he is gifted and I hope his teacher (who is new to the school but had experience as a gifted teacher in public schools) will be patient with him. I'm wondering now if I need to talk to her sooner than later or let her have a couple months to get to know him and then maybe talk about his scores during P-T conferences? I don't want to pounce in the second week of school LOL