The purpose of this study is to determine how levels of ventilation rates and indoor air quality vary in elementary schools in southern Japan. This study is based on field monitoring carried out as intermittent monitoring from summer to winter. The concentrations of Volatile Organic Compounds (VOCs) and the air exchange rates were measured in four classrooms in Kagoshima City. The measurements also included carbon dioxide (CO2) in a selected classroom with occupancy of the pupils. The average air exchange rate of the classrooms measured during summer period was high at 18 h-1, where windows and doors were all open. In winter, the air change rates were relatively low at 1 h-1 since windows were closed. The VOCs concentrations in the classrooms varied from summer to winter due to the changes of the air change rate and the thermal condition. Natural ventilation induced by opening windows had a significant effect on the indoor VOCs concentration in schools.