While it may be common, it certainly isn't universal. I've worked in schools in poor communities that have pushed for good educators. In one of those schools, the push for better teachers was by the students themselves. There are plenty of good kids and good parents in many poor communities.

I'm not sure the opposite is true either, i.e. that expensive homes are a proxy for good schools. I've also worked in schools where the families were affluent, but the environment was toxic due to the behaviour of students and parents.