I don't know about internationally, but in the US it is absolutely about race. White people simply do not feel comfortable living near a critical mass of black

I don't know about internationally, but in the US it is absolutely about race. White people simply do not feel comfortable living near a critical mass of black people, and are even less comfortable sending their kids to school with a critical mass of black people -- and that critical mass is low enough to cause significant racial segregation throughout the nation.