The efficiency of schools diverges dramatically across countries in the OECD and can also vary markedly within countries. These differences in levels of efficiency can be traced to policy and institutional settings. As such, moving to best practice could boost educational attainment and reduce pressure on budgetary resources. This paper assesses empirically the relationship between institutional and policy settings and the efficiency of public spending on primary and secondary education across OECD countries. The analysis builds on two previous papers, which respectively developed OECD-area indicators of educational efficiency based on PISA score data and institutional indicators based on questionnaire responses. The results identify a number of institutional and policy settings that appear conducive to raising efficiency, as well as policies that appear to be detrimental to achieving higher levels of efficiency.