The article presents two key concepts of sociological systems theory – externalisation and structural coupling – and applies them to explain (a) the exponential growth of international large-scale student assessments and (b) the rise of 'policy-relevant' educational research. The author concludes with a comparison between key concepts used in systems theory and those used in comparative policy studies. She identifies resemblances with concepts of pathways in historical institutionalism, the multiple-streams approach and the notion of punctuated equilibrium advanced in the advocacy coalition framework.