You are wrong about Canada, at least. I live next door to a high school and I don't know if there is a cafeteria, but at lunchtime they all seem to be out at the pizza or Chinese takeouts. I also am on the bus with them frequently (not a schoool bus!) and the friend groups are more than half racially mixed. Against your universal assumption of adolescent self segregation I will offer the example of my own sons. The younger out of a group of about 10 friends from grade school up (he is 28 now)two are black, one is Asian and two are Persian (twins with Irani parents). athe rest are white. Of course there is self-segregation invlved but in this case it is pure jingoism. An East Yorker of any colour or creed is superior to anyone from Riverdale, downtown or (gasp) the West End... and as for Scarborough...beyond the pale. I do not hold up Toronto as multicultural paradise because it isn't, and of course kids (and adults) like to be in a peer group with common sensibilities. I am just saying that here, at least, although bigotry and xenophobia do exist, they are not predominant or considered "natural".