Yeah I was one of those people too, one of the youngest in my grade.
So I was always friends with people from lower grades, but because I was anoyed at being young in my grade I'd make friends with people in higher grades to try and not feel left out or something... I dunno
Yeah, well now it's much wider gaps then at school. I regularliy go out with friends maybe 5-10 years older and I have heaps of friends that aren't even 18 yet! Even at work I get on great with the young kids, so maybe I'm really immature deep down too!