Police responded to Saint John's Samuel-de-Champlain school Thursday following a report an armed man was on his way there.
Sgt. Rick Caswell said the school was on lockdown when they arrived just before classes ended for the day.
Several parents went to the school to pick up their children but were made to wait on the road until police gave an all-clear a short while later.
Police remained on the scene while a fleet of school buses left and said they would not leave until the last student was out of the school.
Samuel-de-Champlain has about 600 students from kindergarten to Grade 12.