What the show gets right is the idea that prison populations are self-segregating. In reality, this occurs through the formation of gangs, which often include violent rituals and severe penalties for associating with members outside your race. On the show, these groups seem more like slightly meaner high school cliques, each with the same number of members, which gives the feeling of a perverted Benetton advertisement casting call, instead of a nightmarish playground where you might have to stab someone to fit in.
