School is not yet in session, and no one was injured, said Angela Sisi, principal at Wheeling High School.
Firefighters responded to the fire at around 4:15 p.m. on Tuesday afternoon. Cell phone video shows thick black smoke that came from a tar kettle that caught fire.
The school says the kettle was being used as part of a repair project on the roof.
It was parked by the main entrance and after it caught fire, the flames spread to the building entrance.
The schools interior was not damaged, and there were students and staff in the building for summer programs but no one was hurt.
ABC7 has been told Tuesday's fire will not delay the start of school.
