They reported a smell within their math class and were transferred to local hospitals, according to officials. Stagg, located at 8015 W. 111th Street, was evacuated as a precaution around 1 p.m. Wednesday. Students were escorted to three nearby churches.
Fire officials said a school boiler may be to blame for a carbon monoxide leak, but have not released an official cause.
Several ambulances from various suburbs, including a HAZMAT team from Bedford Park, responded to the call, as did three Nicor trucks.
Students were released at 3 p.m. without returning to the school. School officials say classes will be held on Thursday, starting at 8 a.m. At that time, students should go to their 4A classrooms and retrieve the belongings they left behind during the evacuation. After that, they will proceed to first hour.
Zero hour classes are canceled for Thursday.