The high rate of children becoming ill during school periods as opposed to during school holidays has forced authorities associated with the educational system and labour medicine to carry out regular checks in schools and to assign hygienization tasks. Air quality reports, otherwise completely absent from schools, have been requested. Students have reportedly been confronted with headaches and drowsiness, particularly during the second half of their school day. This paper aims to determine the effects of the most important indoor microclimate indicators - namely classroom air temperature, relative humidity, and CO2 content - on the students' productivity and their health. The study regarding microclimate monitoring in the losifVulcan National College of Oradea, Romania, was carried out in the interval of March 2018-March 2019. The Trotek BZ 30 thermohygrometer was used to obtain measurements in classrooms, and the data on temperature, relative humidity, and CO2 was then centralized and processed. Results show that the microclimate in various classrooms in the losif Vulcan National College of Oradea differs according to room type (computer science laboratory, library, classroom), time of day (during classes or after hours), and number of students.