In free running buildings users restore their thermal comfort usually opening and closing windows. In school buildings the window use is also useful to achieve good IAQ and avoid health hazards among students and teachers. In last decades many surveys focused on this topic, in order to understand which environmental parameters are the main triggers for users' actions. This paper investigates the relationship between window use and environmental stimuli in an Italian classroom. The survey concerned the monitoring of indoor and outdoor environmental variables and occupants' actions on windows to assess if occupants were influenced by the environment and the daily routine. Linear and logistic regression analyses were carried out to evaluate the relationship between variables and actions. The results highlight that indoor and outdoor temperatures are the main action trigger, while the relationship with CO2 concentration is weak. Also the daily routine affected students' actions, in fact the opening frequency is higher during breaks. Findings from previous studies are confirmed and new insight on behavioral pattern for school classrooms are presented.