Air quality and thermal comfort in educational buildings are relevant to ensure proper conditions for learning and to avoid absenteeism. However, keeping indoor spaces in good air quality conditions and within acceptable temperature limits requires energy consumption, which is getting more critical in Europe with the energy crisis after the war between Russia and Ukraine started. Although energy optimization in buildings has been widely studied, trying to optimize both thermal and air quality in educational buildings has not been stated before. This study analyses, through optimization techniques and building models, the minimum energy consumption under different building configurations. Additionally, knowing that the future electricity framework relies on energy flexibility, this study also analyses the effect on the energy flexibility capacity for participating in demand response services to find alternative paths to reduce energy expenses.