A Hamilton high school was plunged into lockdown just before midday today after a young man started threatening staff and damaging the school's property.
Melville High School principal Clive Hamill said he placed the school in lockdown at 11.45am due to "significant concerns for student safety".
A young man had threatened staff, vandalised property and walked around the school in a menacingly and intimidating manner, Hamill posted on the school's Facebook page.
"Despite several attempts by teachers, senior leadership team and the young man's friends, we were not able to stop his dangerous and threatening behaviour."
Police were called and are now investigating.
Hamill thanked the police for their help and praised staff and students for their quick response to the lockdown sirens.
No students or staff were injured in the incident.