Many people assume that sending their child to a private school will boost their academic achievement. That assumption is wrong. As Treasury noted in a report to Finance Minister Bill English about increasing the use of the private sector in education in 2011, recent analysis by the OECD of school performance has found that "public schools tended to outperform private schools in New Zealand after controlling for the socio-economic background of students and schools" (Education at a Glance 2011, analysing 2009 PISA data).
In the report, Treasury advised that it was "sceptical" of the "student achievement benefits that could be gained from introducing more actively competitive mechanisms into the New Zealand schooling system, such as vouchers, removal of zoning arrangements and increasing financial support for private schools. Systems that have pursued these policies have not gained systematic improvements in student outcomes".
It also advised against accepting unqualified teachers in charter schools and pointed out that systems that create a more competitive environment, including using charter schools, do not systematically produce better results for students (Report to the Minister of Finance Treasury T2011/2380: Increasing the use of the private sector).
So what does the evidence show does work to improve education systems?