The low-quality of education in much of the developing world is no secret. The Annual status of education report (Aser), produced by the Indian NGO Pratham, has been documenting the poor state of affairs in that country for several years. The most recent report highlights the fact that more than half of grade five students can read only at grade two level. Similar statistics are available from around the world.

Since 2000, primary enrolment rates have risen from about 80 per cent to more than 90 per cent – that is close to an extra 36 million children in primary school. And there are more than 90 million more children in secondary school now than in 2000. Rising population and, until 2008, growing incomes explain some of this increase. But a large part of the story is about education programmesby governments and NGOs to get more children into school.

There is a common view that in targeting quantity – getting children into school – quality has been sacrificed by not making sure that they learn something once they get there. Overcrowded classrooms, poorly qualified teachers and lack of teaching materials create a poor learning environment, exacerbated by rampant absenteeism among both pupils and their teachers.

We know there are a range of supply-side programmes, such as building schools in rural areas where access is otherwise limited, and demand-side interventions, such as conditional cash transfers, which pay a stipend to poor families on the condition that children go to and stay in school.

Programmes such as Oportunidades in Mexico and the female secondary school assistance projectin Bangladesh have been important in increasing enrolment, especially among girls, in the past two decades. But what is the point if they do not learn anything once they get to school?

A review of the evidence of what works in education, produced by the International Initiative for Impact Evaluation (3ie), paints a more optimistic picture. Pulling together findings from 75 studies, our analysis shows that government and donor education programmes work – not only in getting more children into school and keeping them there, but also at learning more, especially in reading, writing and maths.

The finding surprised me. I had expected to see a significantly positive average treatment effect (the overall average impact of the interventions being assessed) for enrolment and possibly attendance. But I had bought into the children-don’t-learn view enough not to expect a positive effect on test scores, or even the proxy measures of dropout and grade repetition. I was wrong. On average, the interventions have a positive impact on all education outcomes, including learning.

This finding does not alter the facts: most children in most schools in most countries are not learning enough. But our study shows that we know what to do about it. Of course, not everything works. And for most interventions there is too little evidence to be confident. But some clear patterns emerge.

Reducing the costs of education makes a big difference. Several African countries abolished school fees in the past two decades – for example, Malawi in 1994, Uganda in 1997 and Mozambique in 2003. In every case, the move has been accompanied by a large increase in enrolment. Costs are also reduced by conditional cash transfer schemes, and there is consistent evidence of how these programmes get more children into school.

Building new and better schools also helps, as does providing school meals. Existing evidence – which is admittedly rather less than we would like – does not support the position that these programmes increase test scores. But different interventions can.

Increasing teacher resources, including computer-assisted learning, clearly comes out as the most successful approach. Looking more closely at the evidence also gives pointers as to how to design programmes. Just dumping computers in schools will not help. They need to come with age-appropriate learning software, and staff with a bit of technical knowledge to get the machines up and running.

School-feeding and school-based management have been shown to increase maths scores, but we need more evidence to know if there can be a similar impact on reading and writing. For some nutrition interventions we do have strong evidence. Providing iron-fortified vitamin pills to children in rural China, where anaemia rates can reach 50 per cent, had an immediate impact on learning. A C-grade student can be turned into a B-grade student at the cost of a few pennies a day.

The overall message is good. We know what works to get children into school and keep them there. And we have identified a different set of programmes needed to improve learning once they are there. We need to strengthen the evidence base, but we have strong pointers as to where we should be looking.

How will they ever learn? By going to school and by governments taking evidence-based steps to improve the quality of education in those schools.

Download  the 3ie review

Download brief based on this review

(This blog first appeared in the Guardian’s Poverty Matters blog.)