An added police presence Tuesday morning at Walkerville Collegiate Institute on Richmond St. in Windsor.
Greater Essex County District School Board Spokesperson Scott Scantlebury says an old social media post recently resurfaced online.
He says the threat was first received in September and at that time school board officials along with Windsor police felt the threat was not credible.
Scantlebury says all staff and students are safe.
The post read "14 Jan I Kill All."
Photo sent to AM800 news