The Dutch government and School Inspectorate encourage schools to use the student performance data they can obtain from their student monitoring systems to maximize student performance in a systematic and goal-oriented way. Research by the same Inspectorate (Inspectie van het Onderwijs, 2010) shows that students in schools which do so outperform students in schools where data-driven decision making (DDDM) is as yet less developed. The University of Twente developed a training course in which school teams learn to utilize data from computerized student monitoring systems in order to improve instructional quality and student performance. Parallel to the training activities, training effects are studied. The research findings show that the training activities had a positive effect on school staff's DDDM knowledge and DDDM skills. Staff attitudes towards DDDM were already high on the pre-tests and remained high on the post-tests.