All the students and staff at Heritage Regional High School on Montreal's South Shore were released from the building after being locked in for a few hours due to threats.
Longueuil police say a young person was arrested in Chambly, Que., in connection to the threats and the suspect will meet with investigators.
Police are not saying the nature of the threats, only that they were serious enough to shut down the school.
The school's principal, Sujata Saha, says the threats had been made by a person not attending school.
In a statement, she says buses are scheduled to depart at 7:20 p.m. This comes after the building was locked down at the end of the school day and Longueuil police set up a safety perimeter.
"The police have assured us that at no point in time was the safety of your children at risk while they were in our building" she says.
"The police needed to lock the access to and from our school while they conducted their investigation."
Saha recognized that the incident caused concern for parents and students.
"We will debrief with your children next week. Please know that support services are available at the school should your child want to speak to someone," she said.
"As always, the safety of your children remain our top priority at all times."
Throughout the afternoon, police were asking parents not to go to the school, but insisted everybody was safe and uninjured.
The school, located in St. Hubert, has a student body of about 1,300.