Research has shown that data use can lead to increased student achievement (Carlson et al., 2011; Lai et al., 2009; Poortman and Schildkamp, 2016; Van Geel et al., 2016). At the same time, more and more data have become available to schools and teachers. Education authorities are increasingly expected to make use of data (e.g. national assessment data, international large-scale assessments) in decision making regarding education policy and reforms. School leaders and teachers have more data available from classrooms and schools through observations and surveys that they can take into account in individual and collective professional judgment regarding teaching. This is often referred to as data-based decision making, data use for short. This involves the systematic collection, analysis and interpretation of multiple data sources, such as assessment results and classroom observations, to improve education (Schildkamp and Kuiper, 2010).