This paper studies the optimal allocation of resources--in terms of school management, teachers, supporting employees and materials--in secondary schools. We use a flexible budget constrained output distance function model to estimate both technical and allocative efficiency scores for 448 Dutch secondary schools between 2002 and 2007. The results indicate that the average technical efficiency amounts to about 78 percent, implying that, with the given resources, schools could improve students' educational performance by 28 percent. In terms of allocative efficiency, we estimate a 0.65 percent overutilization of teachers while management and supporting personnel are underutilized. The outcomes indicate that, despite the significant variation among schools, the average school is close to the optimal allocation of teachers. (Contains 5 tables and 3 figures.)