It happened at Assumption College in West Brant while the school was being used for sporting events.
Guelph Police are investigating after a family distracted a store clerk and stole a chair worth almost $500 on Monday.
A 21-year-old man has been charged with making a threat that caused police to evacuate Assumption College late Tuesday afternoon.
Police say they began investigating at about 4:30 p.m. after a former Assumption student went to the school and threatened staff and students.
When police arrived at the West Brant high school, they evacuated about 150 students, staff and others, most of whom were there for a Brant County high school boys’ volleyball game.
Police say they secured the school and occupants were ordered to go to the gymnasium where staff members quickly secured all the exits and people were told to find safe places. Some students hid under bleachers.
Someone at the school during the incident estimates there were 10 police cruisers and 50 officers on the scene.
Police are continuing to investigate but believe there is no further safety concerns for students, staff members or the community.
Anyone with information about the incident is asked to contact Brantford Police at 519-756-7050 or Crime Stoppers at 1-800-222-8477.