Police were called to Greater Shepparton Secondary College about 11am to four young people on school grounds.
Two of them were former students, and two had never attended the school.
Police said one of them — an 18-year-old woman — was seen by a staff member on CCTV allegedly “displaying a large knife tucked under her jumper”.
The school was placed into immediate lockdown in line with its emergency management procedures.
One of the group broke off from the others shortly after entry to the grounds, and was found wandering outside near the agriculture area, police said.
The other three were found by police outside school grounds, on Hawdon St, near the car wash.
An 18-year-old Shepparton woman, who has never been a student of the school, was found with what police described as an “extremely large bread knife” with a serrated edge.
The knife was “the length of an adult arm and hand,” a police officer said.
The woman voluntarily surrendered the knife to police when she was challenged by them in Hawdon St, police said.
The woman will be charged with possessing a controlled weapon.
The other two girls with her were not charged, and police said they “didn’t do anything other than wander behind her”.
Police said none of the group went into any of the school buildings, and were only on the grounds for a matter of minutes.
They had been made to exit by staff out a gate near the grassed area at the front of the school.
The school remained in lockdown for about 30 minutes until the all-clear was given.
When asked about the incident, a Department of Education spokesperson said “the safety of students and staff is always our highest priority, and wellbeing support is available for any student who needs it”.
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