External accountability policies have spread fast across various educational systems over the past decades. This research examines the relations of internal and external accountability with students' math achievement drawing on PISA 2012. With a sample of 44 educational systems, of which external accountability policies were identified, the research conducted three-level hierarchical linear modelling (HLM) analyses. This research found that some internal accountability factors had tighter relations with math achievement, while the relations of external accountability policies with student performance were rather tenuous. However, equity of student math achievement was better ensured under strong accountability systems. The results suggest that policy makers of each country should consider strengths and weaknesses of external accountability in their own educational contexts.