A group of Timaru Girls' High School students placed 750 little yellow rubber ducks around Timaru Boys' High School in the early hours of Monday morning. But the boys never got to see the quacking prank - the ducks were confiscated before school began.

School teachers who foiled a quacker of a prank in Timaru on Monday morning have become Facebook fodder, with some commenting that the joke is on the staff.

A group of Timaru Girls' High School students placed 750 rubber ducks on the grounds of Timaru Boys' High School in the wee hours of Monday morning, ready for a good laugh to start the week.

But instead of leaving them for a quack-up, the ducks were quickly gathered up before the boys arrived, with deputy rector Rod Sparrow confirming he collected the toys.

Rector Nick McIvor said he did not mind sensible fun but could not see the fun side to this one.

Despite the ducks being cleared, Jo Brodie thought the joke was on McIvor and his flock.

"I think the prank worked. The joke's on the principal and his minions that ran around the school collecting rubber ducks. Well done girls..." she wrote on Facebook.

Pauline Young also supported the prank.

"Harmless fun, surely. With all of today's negativity and pc crap, surely some plastic ducks on a grass area pose no threat or danger to anyone. Well done ladies."

Gerrie Ligtenberg thought it was "sad really when you cannot see the fun in this".

"I think this is a win for the girls. How on earth are you going to teach boys when you have no sense of humour?"

It is understood other senior staff may also have been involved in removing the ducks.

McIvor said the prank had gone further, with a famous statue on the school grounds also spruced up.

"They also decorated the Jack Lovelock statue with a wig, tiara and clothing," he said.

He was concerned it could prompt retaliatory action between the schools.

In 2014, another group of students plastered underwear and other items along the front of the boys' school.

"We appreciated the apology from the school... it was a mess and we had to clean it up," he said.

When asked on Monday, McIvor did not think he was like the Christmas grinch, pointing out there were other opportunities for the students from both schools to connect.

The prankster girls had asked for their ducks back and were assured they would be returned later on Monday.

Girls' High principal Sarah Davis said she knew nothing about the incident.

The disappointed pranksters asked not to be identified. They "did not want to burn bridges in their last few days of school".