A group of teenagers carrying bats and knives have forced students to hide in classrooms at Canning Vale College in Perth.
The school went into lockdown around 3pm AWST after a group of 15 to 20 males were spotted running through the school grounds.
It is believed that the group were looking for one student in particular - after teachers at the college became aware of this, that student was placed into isolation.
The intruders were chased off the property as police officers arrived on the scene.
The student that was placed into isolation was escorted off the property by police, possibly because of concerns to his safety.
Parents were notified of the event during the afternoon by SMS.