Waterloo Regional Police say they are investigating a threat directed at Cameron Heights Collegiate Institute in Kitchener.
They first got word of the threat on Friday.
Police say it was made anonymously via social media and stated "I'm shooting up the school on September 10th."
The school's Resource Officer, Detectives, and members of the Cyber Crime Unit, continue to investigate the threat and identify the author of the message.
Police are also working closely with the public school board to ensure the safety of all students.
Anyone who has any information is asked to call police at 519-570-9777 or Crime Stoppers at 1-800-222-8477.
"It is unacceptable to make threats, written or verbal, towards anyone." Cameron's Principal, Ray Teed said in a statement posted on the school's website.
"No matter the intention, we take any intimidation or threat of violence seriously and the authors of these threats need to understand that they will be held accountable." Teed added.
The statement goes on to say police will be present at the school on Tuesday and access points to the building may be limited.