FWIW, your ds sounds *very* much (and I do mean *VERY*!) like my ds at 7 years old (and through the first 2 years of elementary school. Even his teachers sound like the same set of teachers... and the WISC scatter is very very similar.
So.... this is my take on it (my ds is now 13 and in 7th grade... and it's been a very long journey to get to this point. It's possible that none of this applies to your ds, but fwiw:
He's not conventionally LD (the gap btwn PS & everything else could be called a written output disorder) and it only arises because he doesn't do his work w/o a teacher at his side prodding him.
Re the gap between PS & everything else "could be called a written output disorder. For my ds, it is a symptom of a very real written output disorder.. and what may seem like not much of a big deal in 2nd grade turned into a huge deal by the time he was in 4th grade. He is still, in 7th grade, years after we knew about that gap in PS and everything else, and after years of remediation, tutoring and accommodations, still struggling with a written output disorder. He's made a TON of progress, and he's a happy kid who's able to benefit from challenging academics at school - but he's still very much a student with a learning disorder who needs support with schoolwork at home and at school.
I would have said (and did say) the exact same thing you've said about your child to describe my ds in 2nd grade: "he doesn't do his work w/o a teacher at his side prodding him." And he didn't. And when a teacher was at his side prodding him, the work he did do didn't match anything I knew he was capable of (it was clear from very early on that he is an EG/possibly PG child). So I was caught in this triangle of us (parents) constantly explaining away classroom behavior as gifted quirks/boredom/perfectionism/whatever, his teacher convinced he was either stupid, lazy, or severely ADHD, and my ds, who had no idea why he couldn't do what people were expecting him to do at school, was seeing other children complete their writing with no trouble, and eventually became so anxious over it all he was having severe panic attacks.
No one was more suprised than me to hear a neuropsychologist explain that my ds had a disability - but he does. I wish he didn't, but he does.
If I were back in your shoes today - I would consider the possibility that there is a writing challenge for your ds. There are things you can do to explore the possibility - I'll list them below. It's not the end of the world, but if he does, providing him only with extra enrichment and challenge isn't going to solve the problem, and chances are it might fall flat and backfire if he's going into a situation where he's expected to be able to write.
This is what I'd suggest -
* Have your ds take the TOWL (Test of Written Language) - this is a common test used to understand specific challenges with written language.
* Consider having your ds evaluated by a Speech Language Pathologist. Chances are that you are thinking why do this? My ds' speech is a-ok... and yep, my ds' speech (verbal) is also a-ok - or so it seems, he's extremely verbal and can clearly speak at a way-ahead-of-age-level of comprehension... about things he knows about. The thing that was very subtle for our ds and passed our radar completely was he was very challenged with generating thought output in either speech or writing when he was faced with an abstract request. It showed up in writing first because there's no way to hide in the classroom... but after a few years when ds was a bit older and was starting to understand himself a bit better he started mentioning the same types of challenge with verbal expression. His initial SLP eval would never have qualified him for help at school, but it showed a large discrepancy in abilities similar to the WISC score, and the SLP who administered the test noted a significant increase in the time required to answer questions on that part of the test.
* Even though your ds is in private school, you can request an IEP eligibility review through the public school and that would be one way to possibly get the TOWL or an SLP eval.
* Consider having a private neuropsych evaluation - this type of evaluation includes ability/achievement testing + more. You didn't mention achievement testing, but if your ds has had either the WJ-III or WIAT achievement testing, it would be interesting to look for scatter in the scores vs the output format of individual subtests - does he score significantly lower on timed subtests? Or on subtests that require handwritten responses?
* Google around for a list of dysgraphia symptoms and see if any of them fit your ds (what I'm getting at here isn't a challenge with knowing *what* to write but just with the physical act of handwriting, which could also make him a reluctant writer). Does your ds have an odd pencil grip? Does he rub his wrists or fingers or elbow after he's written for awhile? Does he seem to get physically tired from writing? Does he have uneven pencil pressure, break pencils, crumble up his papers while he writes? Does he have odd posture while he's writing, or hold his paper or head at an odd angle? Those can all be symptoms of dysgraphia, as well as letter reversals, uneven or erratic spacing of letters, difficulty with punctuation and spelling etc.
Again, there are certainly kids here and elsewhere who have dips in processing speed and who don't have challenges with dysgraphia, writing, written expression, or school. But your ds is having difficulty producing written work at school without prodding, combined with his very large dip in processing speed - which leads me to suspect that it's at least worth looking into the possibility of a written expression LD.
polarbear
ps - forgot completely about the question in the title of your post - "extension or Special Ed".... jmo, gifted 2e kids need both - maybe not full-blown SPED qualification, but a child who has a challenge absolutely needs remediation and accommodation. I think most of the 2e parents I've known have found that you have to start with remediating the challenge in order for your child to then later be able to fully benefit from extension in their areas of strength. Absolutely provide your child with interesting, intellectually challenging experiences as much as you can starting early on, but when there's a time conflict between helping with the challenge or giving extra extension to build on areas of strength, sometimes in early elementary the extension has to take a back seat to getting remediation for the challenge. It's not as grim as that might seem - by really really focusing on remediating in elementary school, we gave our ds the chance to absolutely soar in his areas of strength now that he's past elementary school. One thing to remember is it's not just about the direct skills, but also about self-confidence and believing in your ability - and that's something that most 2e kids need the remediation in weak areas for every bit as much as the actual skills.
