In order to support research on school effectiveness, there is a need for valid and reliable instruments to assess policymaking capacities of schools. Increasingly, policymaking is seen as a shared responsibility of the entire pedagogical team of a school. In this article, data were analysed from a sample of 1,696 (care) teachers coordinators and principals from 77 Flemish primary schools to assess critical aspects concerning validity and reliability of the Policy Making Capacities Questionnaire (PMC-Q). Confirmatory factor analysis indicates that the fit for the model with eight factors is limited. The subscales were found to be strongly correlated and difficult to distinguish, and one of the subscales turned out to be not well captured by the questionnaire. The results indicate sufficient interrater reliability and within-group agreement to aggregate responses to school level. Suggestions are made for further development of the PMC-Q and its use for research and practice.