St. Monica's Catholic School in Barrie's east end was placed under a hold and secure, Thursday afternoon.
The precautionary measure has since been lifted, according to the Simcoe Muskoka Catholic District School Board.
The school, located at 90 Steel St., was placed under hold and secure shortly before 2 p.m., due to an external police matter unrelated to the school, according to the board.
Peter Leon, from the Barrie police department's communications unit, said it was due to a domestic matter nearby that has since concluded.
Board officials tweeted shortly after 2 p.m. that the hold and secure had been lifted by Barrie police.
Under a hold and secure, activities inside the school continue normally, but the exterior doors are locked and visitor access is restricted.
