Existing school buildings in Switzerland that have been designed from the early 1970s typically utilized a modular architectural layout and structural system commonly known as CROCS (Centre de rationalization de d’organisation des constructions scolaires). Such buildings were designed without any seismic design requirements. However, Switzerland is a moderate seismic zone and the seismic safety and lateral stability of such buildings should be carefully examined. There is also a similar concern because of hazards due to induced seismicity. In particular, such buildings could develop a soft story collapse mechanism because capacity design principles were not employed. The aim of this Master thesis is to investigate the non-linear static and dynamic behaviour of a CROCS school located in Switzerland in a moderate seismic zone. Its performance is examined based on nonlinear response-history analysis in the context of Performance-Based Earthquake Engineering. A numerical model is developed using the concentrated plasticity modelling approach to identify its most critical seismic deficiencies. Based on the findings, an optimal seismic retrofit strategy is proposed and evaluated.