Graffiti triggered the evacuation of Saugeen District Senior School late Wednesday.
Police were called just after 3 p.m. Wednesday about the message in relation to a bomb.
The school was evacuated and investigators searched the building.
Police are not disclosing what the actual message was as they are still investigating the crime.
And Saugeen Shores Police Service believes there is no legitimate threat to the safety of the school, or the staff and students.