In this study, in order to analyze the air quality of the indoor environments of schools, we measured the indoor, outdoor and personal exposure concentration level of $PM_{10}$ for 40 classrooms(20 old, 20 new) in chungnam area from June 22 to July 19 and from November 21 to December 30, 2003. 1. Old classrooms contained more dust than new classrooms; the average of respirable dust is $43.27;{mu}g/m^3$ for new classrooms while $53.38;{mu}g/m^3$ for old one. The exposure concentration level of respirable dust in new classrooms were in summer higher outdoors than indoors. The values were indoors $46.71;{mu}g/m^3$, outdoors $50.46;{mu}g/m^3$, and personal $41.62;{mu}g/m^3$. Meanwhile in winter indoors had a higher concentration level than outdoors, the values being indoors $39.11;{mu}g/m^3$, outdoors $34.86;{mu}g/m^3$, and personal $49.01;{mu}g/m^3$. 2. Cr concentration level within dust was slightly higher in summer indoors ($101.50{pm}32.10;ng/m^3$) and outdoors ($100.89{pm}35.18;ng/m^3$) than winter indoors ($85.80{pm}48.95;ng/m^3$) and outdoors ($74.43{pm}38.93;ng/m^3$), but in personal concentration level, winter was higher. The results of this research show insufficient understanding of health risks from indoor air pollution, and shows possible health problems to students from school indoor air pollution. As such, a logical and systematic education program for students about the importance of indoor air quality should be carried out. Also the results of $PM_{10}$ concentration level measurements emphasize the need for regular measurements of indoor / outdoor and personal concentration level. New classrooms in particular needs to be used after measuring pollutants and safety, and requires installation of a ventilation device in all classrooms to improve air quality.