A teenager has been arrested after a threatening email was sent to Dunedin's Bayfield High School, police say.
Armed police arrived at the school after they were alerted to the threat at 8.17am on Tuesday.
The school went into lockdown and police later escorted around 550 students and staff off the premises.
Acting principal Mike Beagley later said a "managed evacuation" had been carried out.
"Our thanks to all parents and caregivers for their support and help in making this run smoothly."
Detective Senior Sergeant Nik Leigh said police searched a Dunedin house on Tuesday afternoon and arrested a 16-year-old youth.
He would appear in Dunedin Youth Court on Thursday, facing a charge of threatening to kill.
Leigh said police were working with the school and further charges may be likely.