race and elementary school

A curious development has happened in the first few months of Kindergarten -- Ben seemingly has joined a group of friends (about 3 other boys) and they're all ASIAN!!! This is interesting to me, as my son has joined what I call the "racial clumping" phenomenon (I'm sure there's a more sociologically correct term), where kids tend to hang out with their own race. His class seems to be about 30-35% white/black/asian and 5-10% latino.

This isn't surprising, generally. Kids tend to stick to the familiar and similar cultures and appearance breeds familiarity, so this doesn't surprise me for most children. HOWEVER, my child has the following working against this mentality:

-He is of mixed race
-We live in a mostly African-American community
-His entire extended family is white
-He has never spent extended time with 100% Asian kids -- they've all been white/Asian mix, white, or black
-I am not culturally Korean -- the most Korean we get is his white father eating kimchee

So what would cause him to be in the "Asian boy" group? Is it because these boys grouped together naturally (I'm assuming they all have culturally Asian parents -- I believe they are all Chinese, based on their last names)? Did they know each other in advance? Did they see my son and accept him into their group based on his looks? It seems that Ben befriended a boy early on and then they all started hanging out together somehow. Since I'm not there, I don't know the ins and outs of it -- I'm just extrapolating from the little he's told me and what I've been able to observe.

I also realize that very little of this matters to children -- it's not in their consciousness. Maybe in their subconscious they are choosing their friends based on race, but it's not their primary motivator. I remember an incident when I was in elementary school when a Jewish kid called me "flat face" and I called him "big nose" -- we weren't being racist, we were just insulting each other based on our observations. I had no idea he was Jewish until I was much older! I actually didn't have a conception of race until I was in middle school. I knew I looked different than my parents, but I wasn't able to process why/how I was different besides the fact that I was born in a different country.

No matter what their race, I am so glad that my son has found friends so quickly at this school -- it's an answer to prayer for me!