Cordons around Otago Boys' High School have been lifted, after the school was evacuated this morning due to an unspecified threat.
Police said emergency services were called at 7.35am following a "threat", resulting in the evacuation of the school as a precaution.
Police and emergency service cordons around the school were lifted just before 10am, having been in place for nearly 2½ hours.
"A search of the school has not located anything of concern,'' a police statement said.
"However, a police presence will remain at the school for the next few hours to provide reassurance.
"Police would like to thank the school and nearby community for their co-operation and assistance as we worked to ensure the area was safe.''
Nearby Arthur Street School, which was also affected by the incident, earlier decided to close for the day.
The incident disrupted the start of exams today, and saw a scholarship calculus exam moved to John McGlashan College and a Level 2 Physics exam has been shifted to St Hilda's Collegiate.
OBHS contacted parents via text message to get them up to date with the unfolding situation, and the school's response was praised by several people on its Facebook page.
All boys were asked to stay at home until further notice, and boys already at school _ including students at waterpolo training _ were looked after by teachers and school staff.
Fire and Emergency New Zealand had two appliances at the scene on standby, and St John had an ambulance at the school as a precaution.