When do in-service teacher training and books improve student achievement? Experimental evidence from Mongolia

This study presents evidence from a randomized controlled trial in Mongolia on the impact of in-service teacher training and books, both as separate educational inputs and as a package. It tests for complementarity of inputs and nonlinearity of returns from education investment, as measured in students' test scores. The result suggests that the provision of books, on top of teacher training, raises students' achievement substantially. However, teacher training and books weakly improve test scores when provided individually. This study sheds light on the relevance of supplementing teacher training schemes with appropriate teaching materials in resource-poor settings.