A planking competition organised by a Rotorua school is being defended by its principal as a safe way to teach kids how to be responsible with the craze.

A Rotorua mum, who did not want to be identified, said she was astounded when she found out Rotorua Intermediate School was running a competition that encouraged planking. However, the principal said the competition was about showing children they could take part in a craze while being responsible.

The woman's son attends the school and she became aware of the competition when she overheard him talking about it with a friend.

"Planking" is the term for the craze involving people laying flat, face down, with arms to their sides, often in public places. The photos are posted on the net.

The craze came into the spotlight when an Australian man fell to his death after planking on the rail of the balcony of a seven-storey apartment in Brisbane.

It then came under fire in New Zealand after a Tauranga Boys' College student was pictured on Facebook planking across a railway track.

The woman said her son and a friend showed her some photos of some students planking up a tree and on top of soccer goal posts.

"It's dangerous. I want it stopped," the woman said.

She said it wasn't appropriate for a school to condone such behaviour and believed parents should have been consulted.

However, principal Garry de Thierry defended the competition and said he was disappointed the complaint had not been brought directly to him.

He said the school had identified planking as a craze and they wanted to teach students they could take part in it responsibly.

"It's about showing [students] you can take part in a craze, but you can do it safely."

Mr de Thierry said the school had spoken to the students about planking and showed them YouTube clip examples of what was and what wasn't responsible planking.

The school also set criteria - it had to be creative and it had to be safe.

Mr de Thierry said students were only allowed to do it within school grounds.

"We're trying to teach kids they can still have fun without the risk."

He said it had created a lot of discussion around the school.

"The kids are really enjoying it."