The Affton School District called off classes Monday after bus drivers found a downed power line on some of the empty buses.
Erica Chandler, a district spokeswoman, said no one was hurt.
The power line fell on buses parked near the administration building at Weber and MacKenzie roads. Bus drivers arriving to work about 6 a.m. saw the line down. The district made the decision to call off school and notified parents around 6:30 a.m.
The line runs between two light poles. A tree and part of a light pole also had fallen on some buses.
"It affected half of our fleet," Chandler said.
The district has about 2,700 students.
At 8 a.m., Chandler said, the district was still waiting for Ameren crews.