Many innovations that are implemented in schools are initially successful, but fail to become part of the schools’ habits and routines. Relatively little research has followed innovations in schools for a long(er) time. In addition, few reforms last long enough to be studied longitudinally. In this exploratory study, the authors aim to find a way to quantitatively measure the degree of sustainability of a data use intervention three to eight years after its initial implementation. Sustainability in this study was defined as ‘…the process of integrating and scaling the innovation’s core aspects in organizational routines that are adaptive to ongoing work, with continuing improvement of results’. A distinction was made between sustainability of the method and sustainability of the underlying goal of the data use intervention. A cluster analysis showed that schools can be categorized into four degrees of sustainability. A general view of the data indicated that the core components were present to varying degrees. Radar charts have been made and provided more insight. The process from organizational routines, and transfer of the intervention from the individual to the institutional level realizing organizational routines differs from school to school. The answer to the question as to whether an intervention has been sustained is not a simple yes or no. Sustainability is nuanced and can come in different forms. Measuring sustainability in a quantitative way contributes new perspectives and insights. With those insights further research can be done.