I was perusing Marginal Revolution (about vouchers) and came across this comment

In other words, even if a child’s chance of going to the state university is not increased by his new school, the kid’s chance of ending up in the state penitentiary is radically decreased. This consideration might not be of primary concern to many who support vouchers, but to those who live in the ghetto, it is of PRIMARY concern. Schools, more than anything, breed gangs. Like the projects of old, when you are FORCED to a geographical location, you make gang recruiting easier – and your kids chances of entering the prison system that much greater.

I saw a lecture by Nobel Laureate James Buchanan many years ago and before he veered off into pure math he said that there were three types of social organization, which he dubbed (something like this anyway), the closed circle, the open circle, and the broken circle. The closed circle is a prison, the open is free association, specifically where members have the right to exit and the right to exile rouge members and the broken circle, which is no association at all.

The Buchanan point came to mind…