A systematic review [1] found no uniform definition of low-cost private schools and little engagement with the concept of sustainable scale up of such schools in the South and West Asia region. The evidence was weak and limited, but concluded that there were benefits of low-cost private schools in more stable contexts, in terms of filling gaps in provision at a lower unit cost. However, such issues as weak governance, corruption and lack of security, found in many conflict-affected states, need to be considered. Private schools can also reinforce inequitable access to quality education by excluding the poorest families who cannot afford the additional fees. Therefore, support given to the sustainable scaling up of low-cost private schools should involve careful consideration of all these factors and the wider political economy of fragile states.

A rigorous review [2] found:

• There is strong evidence that teaching is better in private schools compared with government schools in terms of higher levels of teacher presence, teaching activity and teaching approaches more conducive to improved learning outcomes. There is moderate evidence that parents also perceive this to be true, and that the cost of education delivery is lower in private schools. This, however, may imply lower salaries for teachers.
• There is moderate strength evidence that private school students achieve better learning outcomes than their counterparts in government schools. However since most studies did not account for home background differences, there is an ambiguity about the true size of the private school effect. It is also important to note that better teaching and learning outcomes may not mean adequate when considered in the context that many children in developing countries are not achieving basic competencies across both private schools and government schools.
• There is moderate strength evidence that girls are less likely than boys to be enrolled in private schools, but this is context specific. Private schools tend to be less affordable, and the poorest families are unlikely to be able to pay the fees; if they do, there tend to be other welfare sacrifices. Private schools are increasingly prevalent in rural area, but do not necessarily reach the poor.
• There is moderate strength evidence that states are constrained by a lack of legitimacy, capacity and knowledge of the private sector to implement effective policy frameworks, and concerns were raised in the literature that private school provision may be promoted by states without adequate regulation and controls.
• There was very little and therefore weak evidence to support the often claimed assertion that private schools are more accountable to users than government schools; also, the evidence on whether private schools create market competition and drive up standards across the education system was sparse, contested and therefore weak.  

1. The evidence for the sustainable scale-up of low-cost private schools in South West Asia (2014)

2. The role and impact of private schools in developing countries: a rigorous review of the evidence (2014)