Why is he so different at home and at school? Is he using his high intelligence to help him compensate?
Probably. My DS8/gr3 has a history of sensory issues (he would have had lots of DDs as well). He would do his very best to behave in class and then turn into a hurricane as soon as he left the school.
He has "severe" combined type ADHD. His sensory issues were present at home and the classroom, but as he's gotten older they've faded away (he's never been medicated - we haven't ruled that out but he just hasn't been that challenged or deficient). Last year in grade 2 two he would BURST out of the school like a human hurricane after holding himself together during class time. This year he saunters out like the other kids and on a recent SNAP-IV filled out by his teacher, all of his impulsive/hyperactive/sensory behaviours have disappeared, leaving only inattentive as his challenge.
Note - my DS isn't grade skipped like yours, although he is in French immersion. Isn't it interesting, though, that their behviours change with their environments.
Fyi, re discussion about the sensory stuff (which presented early on with our DS and was problematic in KG & grade 1), the school went right to ASD. To make a long story short, he's been seen by numerous professionals (including a full psycho-ed assessment done by a psychologist) and the general consensus seems to be ADHD (the psychologist said no way to ASD). The school still says yes to ASD, so we're wait listed for yet another opinion.
Anyway, the sensory stuff was like this huge, blaring siren for me, but none of the doctors thought much of it. Sure enough, the behaviours have faded.
What kinds of behaviours does your son engage in? Mine was a chewer (EVERYTHING went in his mouth... the other grade 1 kids wouldn't play with him because he was "yucky" and destroyed so many shirts). Gum has solved this (fyi, he's never had a cavity). Now he's orally very typical.
He also used to love to run and crash into things, as well as jump and land on his knees (shudder). He swore it never hurt. He has this obsessive need to run, as well. He's never been a climber, but anything that could be jumped on was fair game. We exercise him a lot (walking, running, skating, gymnastics, swimming) and this has also improved.
Anyway, there are/were so many more behaviours... (spinning was another huge one) I could write a novel... but basically a) the sensory stuff seemed to be ignored by our doctors, and b) I just give him outlets for it, and it's drastically improved.
(When I say "seemed to be ignored" I mean he's never been diagnosed with SPD.)
I don't know if that helps. Imho, whether sensory issues are from SPD, ASD or ADHD, the "treatment" is still the same.
My feeling about sensory issues is to get the child moving and active, and get his senses what they crave. (Fyi my DS has had the emotional stuff too, which again is improving with age and lots of talking together).
