Vouchers - nice in theory but what about the reality?

The Dom Post today reported that National, ACT and Maori Parties had launched a new proposal for what amounts to school vouchers for the top 5% and the bottom 20% of school students.  The scheme is apparently designed to enable parents of these students to utilise other schools or "providers" where it will help their offspring achieve better learning outcomes.

I don't think anyone is opposed to improving learning outcomes.  Also there are some of us who, as parents,  are sometimes deeply perplexed at the poor performance of some teachers and the powerlessness parents have in the face of the education bureaucracy. However, this new scheme raises some real questions that need to be addressed.  For example what is the likelihood that parents of the bottom 20% of underperforming children will actually be able or willing to undertake the transport arrangements, and change arrangements to enable their children to move to another school for part of the day?  Do they have the money or workplace flexibility to enable that for instance?  If not - then doesn't it raise questions as to whether the real beneficiaruies of the scheme will be the top 5% who are likely to be able to afford to put alternative arrangements in place anyway?

Another question I have about vouchers in principle is that the nature of them tend to shift education towards a system based on market power - rather than educational needs. In that context won't it simply empower those who can afford to top up their vouchers with cash payments or school donations? A high quality public education system has long been part of the kiwi dream. While it may not be perfect are vouchers really the solution to the long tail of educational underperformance? I'm not convinced.