Will Wilkinson is my newest hero and he recently wrote about education! Hurrah!
One complaint about the state giving up control over education is that parents would be free to send their kids to weird culty schools. I agree that it's a problem; some parents would send their kids to schools that are not in the child's best interests. For this to be a decisive objection though, you need to show that state education doesn't let some kids through the cracks in the same way. You donÃ‚t need to look hard to find examples of really terrible government schools, apparently even in rich countries (I haven't been there myself). If the government can't prevent the existence of crappy schools why does it count as an argument against privately provided education? If children receive a better education overall through a voucher scheme it's still a good reason to favor it. We shouldn't be soothed just because crappy government schools shouldn't exist in principle if they do exist in practice.
The same goes for licensing in health care, the vision of quack doctors blinds us to the fact that health care is crap.