This study copes with the problem of ventilation in existing educational environments in terms of indoor air quality (AIQ), comfort and energy consumption. In accordance with international regulations, densely occupied environments such as school classrooms need high air change rates in order to provide sufficient fresh air. Nevertheless, in Italian schools, it is rare to see mechanical ventilation systems or natural systems that are mechanically controlled. This means that it is necessary for the users to control air changes by opening or closing the windows. This aspect often causes discomfort and bad air quality, as well as high energy consumption. This paper presents the experimental results of a monitoring session held in an occupied classroom of the high school ITIS V. Volterra in Ancona, Italy, in winter 2009. Various ventilation strategies were implemented, and performance measured in terms of indoor air quality and environmental comfort. Monitoring included questionnaire assessments. Comparisons were also made with IAQ regulations and energy consumption. Optimised solutions are suggested.