His first-grade teacher (Montessori where he was working at a third grade level) last year recommended he be bumped to third grade. We moved and the new school assured us they would differentiate for him. The second-grade teacher has tried by getting materials from the fourth-grade teacher for him to use but he is miserable and has asked to move to fifth grade.
The psychologist who tested him also thinks it would be good for him though she does not anticipate the school agreeing to it. Neither do I, to be frank, but I'd like to give it the best possible shot.
He is very popular and has lots of friends across the grades but does not have friends who "think like me, Mom."
He comprehends quickly and finishes his tests quickly; his Chinese tests on Friday, for which they allot one hour, takes him about fifteen minutes. I do not know how long it takes the other students. He is currently a peer helper for math, so I think it's safe to say he isn't slowing down the class and in fact, the teacher has asked him to let the other students have a turn answering.
I have read a bit about the processing speed with respect to working memory and I am not convinced it would hold him back.