My children are young for grade, and fairly extreme 2Es.
DS7 is very young for grade, with classmates 2+ years older in some cases. He is very obviously young (chronologically, size, maturity, attention span) and yet wants to talk about topics that friends don't like/understand yet. "On average" he is properly placed-- but there is no "on average," just things that work and things that don't.
How we handle it is to problem-solve issues as they arise. There is not much point fretting over the possibility that things won't fit well later. There is only solving problems that can be solved when they arise.
I will also say that my standards have changed. My kids are not cut out to be "in crowd" people, and neither were DH and I, and yet we are reasonably happy and sociable adults. A lot of parents here micromanage their kids' social lives to make them popular or socially successful. We try to make sure our kids have rewarding experiences with other kids, but we are not trying to put them in the center of the school's social life.
We have seen that in middle school, the kids tend to group themselves more by shared interests (no longer by mom friendships or neighborhoods). This helps a lot. We just have to get through elementary first, which is a much more lockstep experience.
