The purpose of this study was to measure and analyze the concentrations ofvolatile organic compounds (VOCs) and formaldehyde in elementary, middle, andhigh schools where indoor environmental improvements have been completed.Measurements were conducted from March 2021 to June 2023, covering 181classrooms in 42 schools. The results were evaluated by school and purpose,and statistical analyses were performed to identify significant differences.Ethylbenzene, xylene, and formaldehyde showed significant differences amongindividual schools, while only benzene exhibited a significant difference amongclassrooms based on their purpose. This suggests that indoor air pollution isinfluenced more by the building materials used in each school than by thepurpose-specific materials. Although the average values for each school andpurpose were below the standards set by the School Health Act, one locationexceeded the standard for toluene, and six locations exceeded the standard fortotal volatile organic compounds at their maximum values. Despite the overalllow average concentrations of VOCs in classrooms due to the increased use ofenvironmentally friendly construction materials and growing interest in indoorair quality, prolonged exposure could have health implications. Therefore,post-construction, sufficient ventilation is crucial, and schools should manageclassrooms to ensure students can use them safely.