# **6 Conclusion**

In this paper, we analyze which investments most efficiently improve education outcomes. We expand on previous education reviews and analyze 150 interventions and policies across 46 countries using a recently developed unified education measure: learning-adjusted years of schooling. A central insight from this analysis is that many interventions that increase participation in schooling are less cost-effective than interventions that improve the productivity of schooling—–that is, the amount of actual learning gained. Policies that improve the productivity of each year of schooling, such as targeting instruction to a child’s learning level or improving pedagogy through structured lessons plans and coaching, can yield large gains in LAYS, narrowing the gap between high- and low-preforming education systems globally. These results should be interpreted with context in mind: challenges should be identified locally, and the global evidence base should then be used to identify possible cost-effective solutions, which should then be carefully adapted to the local context.

This analysis strengthens the foundation for the use of LAYS as a common metric for the economic evaluation of education interventions. Similar unified metrics have played important roles in public health, macroeconomics, and economic welfare analysis, but to date no reference standard exists for education cost-effectiveness analysis, and approaches to comparative analysis have been _ad hoc_ . Using micro-LAYS to express impact sizes achieves three goals: (a) it places attainment and learning outcomes on a unified scale, allowing interventions to be compared directly; (b) it expresses educational outcomes in terms of an easy-to-interpret measure that improves incentives for policymakers to promote both quantity and quality of schooling; and (c) it identifies levers for countries to close gaps between their current performance and the full years of high-quality schooling that they aspire to. Recent research suggests that policymakers may not reap political benefits from learning gains alone (Habyarimana, Opalo, & Schipper, 2020), yet an additional year of schooling can lead to very different levels of learning (Singh, 2020; World Bank, 2018). Using LAYS as a metric of progress allows a focus on additional years and learning together. At the same time, the LAYS framework also helps make a clear case for future impact evaluations to use standardized approaches to measuring learning, for example by using test scores from internationally applied assessments such as the Trends in International Mathematics and Science Study (TIMMS), the Programme for International Student Assessment (PISA), or the Early Grade Reading Assessment (EGRA). This shift would greatly improve the likelihood that policymakers can make informed decisions about which interventions to prioritize and scale up.

In summary, this paper uses learning-adjusted years of schooling to provide guidance on which policies and interventions are the most efficient investment in education, given the state of evidence and data available today. The LAYS metric has recently been incorporated into large-scale policy efforts to improve education. It is a component of the World Bank’s recently launched Human Capital Index (World Bank, 2019), and is being used by the World Bank, UNICEF, and United Kingdom’s Foreign, Commonwealth & Development Office (FCDO) to prioritize cost-effective 29