School buildings have an enormous impact on students’ health, well-being and educational achievement; they also have an impact on energy consumption and other natural resources. Solar chimneys, solar walls, underground ducts for ventilation, shading, and building orientation were used to improve the indoor thermal environment in a pilot project school. A quantitative analysis was carried out based on field measurements by recording some thermal comfort parameters (mainly air temperature and relative humidity) for one year in the school. The aim was to evaluate the effects of the solar chimney, solar wall and underground duct used in selected classrooms on the indoor thermal environment and compare the results to base case classrooms in the same school. The study provided positive results confirming that the passive environment control system used in the pilot school is highly effective in providing indoor thermal comfort on hot and sunny days. The impact of ground ducts and solar chimneys on cold days was relatively small. Most of the classrooms tested on the three floors of the building were found to be thermally uncomfortable in winter.