And as Grinity points out, I think siblings matter. I can stay out of learning partly because my kids have similar siblings and can play chess against each other all day, teach each other about books, computer games, even math. If I had an only kid or a kid without similar age siblings, I expect I'd be forced to be more involved.
I'd go with the personality thing more than the sibs regarding learning. DS13 is an only. He makes friends with everyone but does particularly well with kids his age and their younger siblings. He is always with friends and I hardly see him after school. He just takes care of himself--no siblings needed. And he gets plenty of adult time over meals and at bedtime to fill that need for mature conversation and he doesn't have to compete with siblings for it.
I think for all of our kids, we want them to have a good childhood. For me this means having friends, learning stuff, and playing. Just because a kid can learn at a quick pace doesn't mean that they necessarily should, especially if the learning time interferes with friendships and play. On the other hand, being held back from learning what they want to learn (or are driven to learn) is a serious problem. So is being placed with kids that they can't be friends with. So we each do a balancing act. Are they in a situation where they have real friends (or at least one close friend) regardless of the age difference? Are they able to play in a way that truly makes them happy, even if it doesn't look like play to other parents? Do they have down time and time to explore their interests? Are they learning? Are they learning how to deal with real challenge? The solution to this balancing act will look different for each of us.
