Sergeant Steve Watt, of Queenstown, said a police investigation had revealed up to 15 shops in the CBD were hit on Saturday.
"Mostly clothing and sports shops, but also a number of souvenir shops.
The items have largely been retrieved and returned to the shops," he said.
The 16 boys involved in the shoplifting, aged 14-17 and part of a group of about 30 pupils from Xavier College, in Melbourne, Australia, had been caught during their last day in town after an R&R Sport staff member became suspicious of their behaviour and confronted them.
Xavier College is a boys' Jesuit school, one of Victoria's most elite Catholic colleges, with fees of up to $22,000 or more a year.
Upon their return to Melbourne on Sunday, the boys were met at the airport by their principal, Dr Chris Hayes.
"We very, very much regret their behaviour. We are quite gutted by what they've done," Dr Hayes said.
"I chose to make sure that I was at the airport to meet the 16 students and their parents to inform them of how disgraceful this behaviour was, and therefore to inform them that they would be suspended until further notice."
Dr Hayes said the boys narrowly avoided more serious legal consequences because of their teachers, who interviewed all 30 pupils on the trip and identified the offenders.
They were made to return the goods and apologise to shop owners.
Compensation was paid for damaged goods.
"The boys who were caught seemed very embarrassed.
"I do not pity them for any consequences, and they should be ashamed of themselves for bringing their group and their school into disrespect," Dr Hayes said.
Sgt Watt said the thefts were committed between 2pm and 6pm.
When police got involved, the boys were found to have stolen clothing and souvenirs worth about $6000.
The incident was "definitely out of the ordinary", Sgt Watt said.
"Back in 2006, we had a similar case where Australian youths on a school trip were caught stealing.
"But to have such a large number of youths committing a spate of thefts is quite unusual."
The boys were not charged for the thefts due to their age and the fact the goods had been returned or paid for.
Sgt Watt said they had been given an official warning.
Their names and passport numbers had been registered, to be flagged for further consequences in case they got into trouble in New Zealand in the future.
