for girls, at 0.52 standard deviation. None of these differences is statistically significant at standard levels (Table 2). These are sizeable effects which are the equivalent of more than 2.5 years of additional schooling in the business‐as‐usual setting in many low‐ and middle‐income countries (Evans and Yuan 2019).

What are the most effective interventions for girls?

To summarize the most effective interventions for girls, in this section we present the 10 access and learning interventions with the largest effect sizes and seek to understand their attributes. We contrast these with the 10 least effective interventions in terms of access and learning outcomes. An alternative approach would be to carry out a formal meta‐analysis: As the results demonstrate, there is a great deal of variation within categories of interventions (such as cash transfers), such that taking the average effect of a category is unlikely to yield meaningful insights.<sup>10</sup> Because we code each estimate of the impact of an intervention separately, the fact that one estimate appears in the 10 most effective or least effective does not mean that all estimates of the impact of that intervention are among the most or least effective.

# Access

The 10 studies that report the largest impacts in improving access to education for girls report greatly improved girls’ participation in school, with an average effect size of 0.74 standard deviation (Table 3). Three of the 10 are girl‐targeted interventions, including cash transfers to girls who had previously dropped out of school – conditional on school attendance in Malawi (Baird et al. 2016), improving school water and sanitation systems in Kenya (Garn et al. 2013), and providing private school subsidies for girls in Pakistan (Kim, Alderman, and Orazem 1999). Six of the general interventions are similarly related to offering cash for education in different countries (Eyal, Woolard, and Burns 2014; Maluccio, Murphy, and Regalia 2010; Edmonds and Shrestha 2014; Benhassine et al. 2015; Duflo, Dupas, and Kremer 2017), building village schools in Afghanistan (Burde and Linden 2013) and another intervention is focused on malaria prevention in The Gambia (Jukes et al. 2006). Altogether, six of the ten involve cash transfers, and one more – subsidies in Pakistan – similarly also involves reducing the cost of schooling.

These top interventions demonstrate that reducing the cost of schooling is likely the single most effective way to bring girls into school. Most of these are conditional cash transfers, although fewer unconditional transfers have been tested. In addition, reducing indirect costs – such as the commuting distance to school for girls by building village schools – has been effective in increasing access. Note, however, that one unconditional cash transfer – without a schooling condition – is among the less effective interventions (Table 4) (Baird, McIntosh, and Özler 2011). Improving health conditions through either better sanitation facilities or controlling malaria tends to attract more girls to school as well.

> 10 Analysis of previous meta‐analyses of education interventions suggests that high heterogeneity within categories limits the predictive power of meta‐analysis in education (Masset 2019).

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