The black kid does not associate with his white (I think there are two Indian kids too) friends and only hangs around with black friends. That's all well and good, friends change over time, maybe he does have more in common with those friends colour aside.

Black aren't just white people with a different skin color, they have their own very different values, behavior, and culture. It can be hard to even decipher black vernacular. Blacks who hang out with whites and adopt white values and customs, just like in slavery days, get ostracized by their own for being a "house nigger."