might not be the most efficient tool for this specific purpose. More broadly, our analysis reveals the importance of focusing on policies and interventions that improve the productivity of schooling, rather than solely providing additional schooling.

In Figure 4 we show the full set of 150 studies from 46 countries, highlighting the subset of impact evaluations that include cost-effectiveness data.<sup>12</sup> The first important takeaway from this figure is that, by and large, the subset of interventions with cost-effectiveness data are not systematically biased towards high or low impacts, although within each category the studies with cost-effectiveness data may skew one way or the other. This figure further enables us to assess LAYS gains in absolute terms, rather than per $100, and decompose whether an intervention is cost-effective due to being effective, cheap, or both. For example, health products are moderately effective in improving outcomes, with up to 0.2 LAYS gains per child, but are cheap. Thus, in Figure 3 we see the modest absolute gains translate into up to 10 LAYS gains per $100 per child, marking these health interventions as highly cost-effective. Other interventions are highly effective but expensive, and therefore less cost-effective. Giving merit-based scholarships can yield up to 1 LAYS, but since this policy is relatively expensive, it is less cost-effective than the health programs, delivering 3 LAYS per $100 at the upper end of the distribution of studies. Finally, Figure 4 also includes a new category: nutrition interventions (such as school feeding), which did not enter the cost-effectiveness analysis in Figure 3 due to a lack of cost data. We observe that school feeding is relatively effective in improving LAYS, although with high variance. Taken together with the findings in Figure 3, this indicates that health and nutrition interventions can translate into meaningful education outcomes.

# **4.2 Specific cost-effectiveness studies**

## **4.2.1 Effectiveness and cost-effectiveness**

Next, we examine specific interventions to explore the degree to which aggregate patterns might parallel more granular ones or reveal underlying heterogeneity. Figure 5 shows results for absolute LAYS gained by intervention and country for the studies that include cost-effectiveness data. The top ten performers are: a combined intervention with improved pedagogy, para-teachers and targeted instruction in The Gambia (4 LAYS); the Campaign for Female Education (Camfed) program in Tanzania—a holistic program that includes scholarships and mentorship for girls along with school materials and training for teachers and parents (1.1 LAYS);<sup>13</sup> Tusome (the Kiswahili word for “Let’s Read”) in Kenya—a program that provides textbooks, teacher coaching, and teacher training (1.04 LAYS); building village-based schools in Afghanistan (0.74 LAYS); computer-assisted learning (CAL) in India (0.43 LAYS); community-based preschools in Mozambique (0.41 LAYS);

> 12In Appendix C we complement our data with data from the 2023 GEEAP report (Akyeampong et al., 2023) and compare impact sizes in Figure C2.

> 13CAMFED does not only provide financial support in its program; the breakdown by type of service provided by CAMFED in the paper does not reflect CAMFED’s main offering but rather illustrates how various program offerings might operate together to inform other programs.

19