Earlier quoted context omitted.
What argument are you making that doesn't apply if you replace education, schools and vouchers with food, supermarkets and food stamps?
I bet people buy crappy foods (chips and soft-drinks) for the children when they use food stamps. So there is some similarity. The difference? People have a fair idea as what good food is. Also, education is vulnerable to getting derailed by optimization for tests. And the testing will most likely be controlled by the state. I would worry that big mass-market voucher schools will specialize in marketing, cutting cost…
But I'm less pessimistic than you about people's abilities to make good decisions especially when their children are involved. At least their motivations are better aligned than the government's with their children's interests. Teacher's unions?