A research project aimed at investigating IAQ and thermal, acoustic and visual comfort was carried out in Italian high school and university classrooms. The investigations were performed through field campaigns during regular lesson periods consisting of subjective surveys and measurements. This work focuses in analysing the results from the IAQ investigations at four high schools of Provincia di Torino during the heating period. Measurements were addressed to evaluate the air change rate through the tracer gas technique, the air permeability of the building envelope through the blower door technique and the indoor air quality through monitoring the CO2 concentration. Results from measurements were compared with the requirements from Italian standards and regulations for school buildings. At the same time, questionnaires were filled by students in order to qualify the perceived air quality.