This case study explores the role of attainment targets as a means of systemic quality assurance in Flanders (Belgium), an education system whose governance structures and processes are characterised by high decentralisation and the participation of multiple actors. The analysis identifies a number of key issues in the design and implementation of the attainment targets, such as difficulties in creating a common understanding and participatory governance not leading automatically to teacher ownership of the attainment targets. Three processes that were particularly challenging included the deployment of a whole-of-system approach for implementation, capacity building and the creation of a culture of evaluation. For the future, it is essential to open up participation processes to a broad range of stakeholders. Furthermore, key stakeholders should join forces in setting a shared agenda, creating momentum in implementation and raising capacity across the system, especially in new modes of teaching and assessment.