End-of year school pranks are raising concerns among Dunedin police who say it may only be a matter of time before someone is seriously injured.
School is finished for senior secondary school pupils who are now studying for NCEA and Scholarship exams which begin on Friday.
Pupils annually play pranks on each other to celebrate the end of the year, and many see it as a rite of passage.
Acting Senior Sergeant Dave Scott said there had been several reports of high jinks and pranking by school pupils in the city during the past three days.
Pranks being reported across the city included pupils from various secondary schools filling school hallways with balloons, covering cars in bubble wrap, and putting burning excrement-filled paper bags on school boarding hostel doorsteps, Mr Scott said.
However, there had also been more serious reports of secondary school age pupils shooting fireworks at each other around the city.
"There seems to be a bit of Thomas Foolery going on this year.
"It's all fun and games until someone loses an eye.
"Sooner or later, some one is going to get hurt if this behaviour continues."
He called for pupils to be more sensible and courteous to avoid injury.
The most recent police callout was to Otago Boys' High School where about 17 senior pupils were letting off fireworks on Sunday night.
Mr Scott said Dunedin Police were called to the school by a member of the public about 10pm, to find cling film had been put across the school's main entrance and several cars in the car park area had been covered in bubble wrap.
Mr Scott said the principal was called, but pupils were moved on and no charges were laid.
Otago Boys' High School principal Clive Rennie said the Year 13 pupils had been given permission by the school to spend the night on school grounds, to let fireworks off and celebrate the end of their school year.
The aim was to make sure they acted sensibly and were courteous to neighbouring residents.
"You're not going to stop them, so the best thing is to try and control them.
"It was all pretty harmless."