The school was evacuated, and students and staff were sent to nearby North Toronto Collegiate.
Canine officers and their dogs could be seen outside the school Friday morning. Police said they received a call around 6:05 a.m., but neither they nor a TDSB spokesperson could confirm the nature of the threat.
Police closed three roads in the area for their investigation. Mount Pleasant Road was closed around Roehampton Avenue, the northbound lanes of Rawlinson Avenue were closed from Eglinton Avenue, and Broadway Avenue was closed between Rawlinson and Mount Pleasant.