Windsor police are at Walkerville Collegiate Institute after a threat was made towards the school.
A spokesperson with the Greater Essex County District School Board says a message was received threatening the well-being and safety of staff and students at the high school on Richmond Street.
The board says police were notified immediately and deemed the threat to be low-risk.
Police will remain at the school until dismissal.
According to the Windsor police portal, officers were called to the school for a bomb threat.