An increasing number of countries are adopting accountability systems in education that rely on the external evaluation of students' learning outcomes through standardized assessments. The international dissemination of this form of accountability, often known as test-based accountability, does not imply that exactly the same policy is adopted everywhere. Accountability reforms, as any other globalizing policy model, are context-specific. The concrete form that accountability reforms adopt is contingent on a range of political, historical and institutional conditions, and to policy-making dynamics and logics that operate at multiple scales. This paper analyzes the trajectory of accountability reforms in two Spanish regions, Madrid and Catalonia, from a comparative and multi-scalar perspective. Based on document analysis of media and official sources, and exploratory interviews with key informants, the paper shows that, although these two regions have pioneered the adoption of test-based accountability reforms in the Spanish context, their accountability systems have evolved quite differently. While accountability reforms in Madrid have been oriented toward the promotion of school choice and competition, Catalonia has adopted an uneven lower-stakes accountability approach with multiple ramifications. In this paper, we explain how and why such diverging trends have been possible within the context of a common general regulatory framework.