Developing or specializing existing process schedulers for new needs is tedious and error-prone due to the lack of modularity and inherent complexity of scheduling mechanisms. In this paper, we propose a framework based on a Domain-Specific Language for the implementation of scheduling policies. This framework permits the installation of basic scheduling policies, called Virtual Schedulers, and the development of Application-Specific Policies, which tailor a Virtual Scheduler to application-specific requirement- s. We illustrate our approach with concrete examples that show how specializat- ion and reuse of scheduling policies can be accomplished while retaining OS robustness.