You touched a nerve. The Champaign, IL school of choice system is broken beyond repair. I googled the Milwaukee one. It looks like they may have a better system. Maybe I will do more research and try to lobby for change... In Champaign, parents submit 3 schools in order of preference and then a weighted lottery determines which school your child goes to. You have a better chance of getting into neighborhood schools. They also ensure that each school has at least a certain percentage of African American students (a stipulation of a lawsuit resulting in what is known as the "Consent Decree"). And you get sibling preference (no guarantee) if your childs sibling is going to a particular school.
Lots of middle class people have moved to (or moved into) the suburbs to avoid the whole situation which has actually lowered the quality of the schools (or at least the test scores).