The potential of learning starting points (Lernausgangslagen; LAL) is known, but so far it has hardly been used. This is where the LAMBDA project comes in. In close cooperation with school partners in Lower Saxony, it uses a design-based research (DBR) approach to investigate how primary school teachers, initially using the subject of mathematics as an example, use data from LAL surveys for data-based school and teaching development, what support needs arise and how systematic quality development processes at the teaching and school level can be initiated through needs-oriented qualification measures for various actors. The participatory involvement of school stakeholders and the competence centres for regional teacher training and the sustainable change in control processes that this involves is central to the LAMBDA project.