We aimed to assess the association of household and classroom determinants with students’ school absence due to respiratory tract infections (RTI) among 253 students (4-11 years) of 20 classrooms. We collected 71 absences; RTI incidence was very high during the study period, 17.5-33.1 cases per 100 population. Having someone else at home with respiratory symptoms was the most significant epidemiological factor (OR=9.12, CI 95%=2.54-33.39), suggesting that households are crucial for the transmission of RTI to the children. A positive but not statistically significant association was observed between higher median levels of CO2 and respiratory-related absences (OR=1.2, CI 95%=0.98-1.46).