Primary school teachers face a great degree of heterogeneity in their daily teaching. Identifying the individual learning needs of their pupils and finding suitable solutions can be challenging for them. Digital learning platforms can offer support here: If digital learning platforms are used for practicing in class, teachers have a wide range of data about their students’ learning process at their disposal. With the information that teachers gain from the data, they can derive individualization and differentiation measures. Research on data-based decision making shows that data can be used for decisions in the school and teaching context. There are already approaches for modeling the use of data for decision-making in a circular and process-based manner. For the German-speaking context, however, the process-based use of digital data for instructional design is still widely unexplored. This paper introduces an exploratory study that contributes insights into how teachers use data from digital learning platforms to inform their teaching and how this use can be described along the circle of data-based decision making. To answer the research question, a qualitative research design with a method triangulation of interviews, thinking aloud and observations was used. The results show that the use of data from digital learning platforms by primary school teachers can be described along the five steps of data-based decision-making, but that there are inter-individual differences between the teachers. For example, some teachers only take a look at the data provided by the learning platform in a dashboard without using it further. Other teachers also interpret the data and derive implications for their further lesson planning. The findings from the interviews, the thinking aloud method and the lesson observations are combined, discussed and implications for educational practice and research are derived.