I don't completely disagree with you, but where's the incentive for a government to give you vouchers to spend on non-governmental education, directly taking away funding from the schools the same government is responsible for managing?
If it was a different pool of money, I get it, but -- speaking specifically about the Bay Area -- one of the reasons public schools have suffered is because of attrition toward parochial & private options. When school attendance shrinks, so does funding, which creates a downward spiral of performance in many cases. And it isn't even that all the private options are superior, but because public school funding is dependent on attendance, they detract from the capability & capacity many of these schools have to deliver high quality education. I'm sure it isn't unique, but I've never lived in a place that had such a high proportion of kids in parochial & private schools, and it absolutely does harm the public schools. Compare this to somewhere like Massachusetts, which is equally progressive, treats teachers equally well (better), and has much higher performing public schools -- largely because fewer families with means to pay for private actually do, and those kids & households further support the teachers and administration of their neighborhood schools.