A man who claims his son was assaulted by a teacher at a Palmerston North school has had his accusations rejected by police and the school's board of trustees.

Maurice Wairau, who said his 7-year-old son was subjected to physical and psychological abuse during his two years at the school, took to the street to demonstrate his anger yesterday morning.

Mr Wairau has since taken his son out of the school, but he still stood outside yesterday holding a placard condemning the teacher , and stating the school had done nothing to rectify the situation.

Police and the school said there was no evidence to support the complaint.

Mr Wairau said that over a three-month period he had complained to the school, Child, Youth and Family and police about the alleged abuse.

"I've been through the right procedures and no-one's listening."

Mr Wairau said his son had his wrist grabbed and arm twisted by a teacher.

Palmerston North area commander Acting Inspector Brett Calkin said the matter had been investigated by police when the assault complaint was made in May.

"We decided at the conclusion of the investigation to take no further action," he said.

The matter was referred to the school's board of trustees.

"The school has also followed their own due process and have now thoroughly investigated the complaint and reached the same conclusion as the police," a joint statement from the school and police said.

Acting Senior Sergeant Phil Ward said that Mr Wairau obviously felt aggrieved about the situation.

"He's perfectly lawfully entitled to be here doing his one-man crusade," Mr Ward said.

"We've advised him on perhaps some other ways he can [be heard], which may be more beneficial to Maurice than standing outside the school with a placard, but that's over to him."

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