In theory parents gain access to a better school to enroll their kids and bad schools bleed enrollment. It's not a magic solution to under-performing schools. A

In theory parents gain access to a better school to enroll their kids and bad schools bleed enrollment. It's not a magic solution to under-performing schools. And when it does deliver results it does so by undermining the "public" part of public schools. It increases time and transportation costs. Some parents prefer that the local school be improved instead of replacing it. Alternatives like charter schools use selective admission. When you don't have to accept disabled, non-English speaking, or misbehaving kids it's easy to show higher test scores, graduation rates, and post-graduation outcomes. This leaves the public schools with the bottom of the barrel students. The death spiral is complete once public schools no longer enroll a cross section of the area they serve and only function as a welfare service. Everyone wants the best for themselves and their kid. That means buying housing in the best district they can afford. Once they're in they don't want lower socioeconomic status people to move into their neighborhood or the district to annex poor areas.