South Bruce OPP were informed about the threats Thursday afternoon just after one.
Kincardine District Senior School was placed under hold and secure while investigators track down the source.
It was lifted around 2:45 allowing for the resumption of the school schedule.
A 17-year-old from Kincardine was taken into custody and is being held until their next court appearance.
Police say this was an isolated incident and there is no threat to public safety.