Based on a simulation model, this chapter analyses the effect of limiting structures within the educational system, if action is taken through educational policies aimed at improving the performance of the educational system. The focus is on the scope and possibilities of educational policies. First, the concepts of model and simulation are briefly introduced. Then the simulation model is developed from theoretical considerations and from the inequality of educational opportunity (IEO) model by Boudon, which constitutes a hierarchical system of graduation levels, possibly organized in vertical columns. The actions taken by educational policies are differentiated into those which are concerned with the social origin of the students (i.e. promotion of a specific social class), and those which treat the (however developed) talents of the students (i.e. promotion of gifted individuals). The performance of the educational system is evaluated in three ways: according to its ability to increase the general number of qualifications attained, its ability to decrease the inequality between students of different social origin, and its ability to promote excellence, that is, the proportion of talented students who graduate. The simulation model can thus answer questions such as whether the promotion of social classes rather than the promotion of talents increases excellence, or whether an early branching in the structure of the educational system decreases the output of qualifications, among others. Some results are unique, but others indicate a range of actions available to educational policy.