© 2021 Elsevier LtdWe study exam timetabling problem (ETP) and supervisor assignment problem (SAP) of a vocational school offering associate level degrees in a university. The school has seven departments and plans almost 170 exams in each semester. We propose mixed integer programming (MIP) models for the ETP and the SAP. The optimal solution for ETP of the school is not attainable in two days with a commercial solver. We propose a decomposition method which is able to solve ETP using an open source solver in less than two minutes. The MIP models and the solution method are embedded into a web based decision support system (DSS). Using this DSS, a complete timetable can be prepared in less than two minutes by an average end-user.