.Research shows that most teachers hardly use any data for the improvement of their practice (Schildkamp & Teddlie, 2008). Therefore, a so called data team intervention was developed and piloted to support schools in the use of data. Thedata team is a team, consisting of 4-6 teachers, a data expert, an (assistant) school leader and an external facilitator from a University, who work together to solve a certain educational problem, following a structured approach (see Earl & Katz, 2006). This approach involves: defining the problem, coming up with hypotheses concerning what causes the problem, collecting data, analyzing and interpreting data, drawing conclusions, and implementing measures to improve education. Five data teams were followed during two school years. An example of the problems these teams tried to solve is low mathematic achievement in the lower grades of secondary education. The extensive data from meetings and interviews were analyzed using the program Atlas-Ti. The results of the pilot show that data teams can be effective in two different manners: (1) a data team uses data to solve a problem, thereby improving education and (2) data team members demonstrate learning gains on how to use data to improve their work (e.g. professional development).