In Chile, the vast majority of educational buildings possess neither heating nor cooling systems that regulate temperature and thermal comfort in classrooms. Therefore, indoor temperatures can increase or decrease considerably in specific periods during the school year, thus preventing students from carrying out their academic activities in a suitable environment. For this reason, the present investigation evaluated thermal behavior and took as the unit of analysis each of the five passive design classroom prototypes from the "Energy Efficiency Guide for Educational Establishments" (Guia de Eficiencia Energetica para Establecimientos Educacionales). The study demonstrated the level of thermal comfort in the classrooms in the current climate context. Additionally, comparisons were made to evaluate the vulnerability of these spaces in the face of future climate change scenarios for the years 2020, 2050 and 2080. Lastly, the classrooms with the highest number of hours of thermal comfort were selected so that these can act as models for new educational projects.