This article uses a policy scientific approach to reconstruct assumptions underlying the Dutch Educational Supervision Act. We show an example of how to reconstruct and evaluate a program theory that is based on legislation of inspection. The assumptions explain how inspection leads to school improvement. Evaluation of these assumptions is used to predict the (in)effectiveness of this legislation. The article concludes by discussing the advantages and drawbacks of this kind of approach as a starting point for impact and effect studies. As the program theory of inspection includes elements common to other kinds of educational interventions and reforms, these elements can also be considered for other types of program theory.