It's easier to get away with things such as premarital sex, multiple partners, & competing for the alpha (animal behavior) in the school system. Parents aren't well integrated in that setting. Adults who experienced the same sins are afraid of a light shining through on the whole thing, so they tend to support it. However, if education were handled at a neighborly level, we'd learn much more, have better relationships, & sin less. It's easier to learn in an environment with less social problems & more common interests. You'd have to be wise about selecting your neighborhood tho, as segregation will always be a part of life. You can't expect religions and races to easily attract everywhere. Some areas will have lots of integration if that's your thing, and some won't. Really, segregation isn't a sin if for only the purpose of familiarity. It isn't a sin to integrate also, but it wouldn't be suggested for integrating religions. At a neighborhood level, there's infinite possibilities tho.