If there's any age group at all I interact the best with, it's babies. I've always been that way and I don't know why. And parents have spontaneously told me they've never seen their babies react as well to a new person as they do to me, so apparently it's not my imagination. My mother always arranged for me to play with other people's babies because I got along so well and without as many social problems.
I think when kids get older than infancy they get into far more complicated games, and social stuff, and so they tend to vary as much as adults do in terms of how they react to me. I remember when I was 18 or so I watched someone else my age babysit for older children, and she was very adept at figuring out the flow of pretend games and going along with them, even when they took seemingly bizarre and improbable directions all of a sudden. I was impressed but knew I could not do that.
I have never really had to relate to children-as-a-group since I was one, though, because most places are not as relentlessly and artificially age-separated as schools are.
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"In my world it's a place of patterns and feel. In my world it's a haven for what is real. It's my world, nobody can steal it, but people like me, we live in the shadows." -Donna Williams