A quick-thinking teacher in Etobicoke may have saved her students from serious injury when she ushered them out of a gymnasium minutes before the ceiling collapsed.

Part of the ceiling caved in at Etobicoke Collegiate Institute just before 10 a.m., said Chris Broadbent, manager of health and safety for the Toronto District School Board.

“The teacher . . . and the students in the gym noticed some dust coming down from the ceiling, so they decided to move out of there,” said Broadbent. “Shortly thereafter, a section about [a] third of the size of the gym came down.”

The debris was a combination of plaster, wood and drywall, he said, and covered an area roughly three by eight metres in size.

No one was injured.

Students were sent home and teachers were sent to another school to finish off their day.

Broadbent was on the scene Tuesday, helping to determine the cause of the collapse.

“We’re doing some air testing to make sure everything’s fine inside the building,” he said.

The school district said Etobicoke Collegiate will be open Wednesday.

With 1,311 students, it is one of the largest high schools in Toronto’s west end. The school was built in 1928, and according to the school district, the gym is part of the original structure.