How do we improve schools so that kids learn more?

Philanthropists in the US have spent hundreds of millions of dollars promoting massive overhauls of the education system, often without improving test scores even a bit. Investing in “small schools” didn’t produce the hoped-for gains; neither did pushes to video and evaluating teachers or personalized learning programs. Educators, meanwhile, have protested that test scores don’t even measure the thing we really care about, which is whether students are successfully learning.

Lots of things have been tried to improve education in the developing world. Nonprofits, governments, and researchers have bought students uniforms, paid their scholarships, bought them menstrual products, built more schools, purchased textbooks and technology for schools, paid to reduce class sizes, trained and mentored teachers, and much more. Research suggests that many of these interventions make a difference. But figuring out which makes the biggest difference — and which are cost-effective enough to be worth investing in — is extraordinarily hard.

That’s the subject tackled by a new working paper from the World Bank Group, “How to Improve Education Outcomes Most Efficiently? A Comparison of 150 Interventions Using the New Learning-Adjusted Years of Schooling Metric.” The paper lays out a simple problem: We have an enormous wealth of research studying the effects of school interventions, but not much chance to compare the programs and figure out which one works best.

Investing in teachers is strikingly cost-effective. It’s popular to help students in poor countries by building schools, buying them school uniforms or textbooks, or paying for scholarships. But, the researchers find, popular interventions like these do not compare favorably to ones that focus on teaching. If we want to improve schools, the most cost-effective approach is getting teachers professional development and training.

Read the full article about investing in teacher development by Kelsey Piper at Vox.