A mother who beat her 10-year-old child up to 15 times with a piece of hosepipe for wagging school has been sentenced to 15 months in prison.

The sentencing judge said brutal beatings of children under "the guise of chastisement are almost a daily occurrence in South Auckland".

Manukau District Court Judge Roy Wade said the beating in May this year was breach of trust and a brutal assault on a child by his own parents.

"It is not only a brutal assault, it was a carefully planned and premeditated assault with a weapon being specially cut for the purpose, the family being gathered together and forced to watch while the beating was administered".

The woman, referred to as Mrs N to protect her son, pleaded guilty in July to assault with intent to injure. Her husband admitted injuring the child with intent to injure.

The woman was last year sentenced to six months of supervision for assaulting one of her older children, also for missing school.

The judge said the mother's performance under supervision showed him that she was "simply unprepared to acknowledge the brutality of what she did or to do anything to mend her ways".

The summary of facts in the case said Mr and Mrs N, who had eight children ranging in age from two to 18, had been told by the boy's school he had been absent for several days.

The parents discussed the boy's behaviour and then Mrs N cut a length of hose from the garden hosepipe.

Mr N cut it to a shorter length, to "make it in effect a whip" and put it inside the house for when his son returned home.

When the boy got home, the family were brought into the sitting room to watch the punishment. The boy admitted to wagging school and his mother picked up the length of hose and struck him around his legs, arms, back and head between 10 and 15 times.

"Quite naturally, the victim attempted to protect himself by covering his head and his arms, but then Mr N took the hosepipe off his wife and struck him several more blows on his legs," the judge said in his sentencing notes.

The boy fled to the home of a neighbour, who phoned the police, then took him to the Otara police station.

Judge Wade said the boy had numerous welts and extensive bruising on his body from the assault.

Judge Wade said the statue of Justice above London's Old Bailey court carried the inscription: "Defend the Children of the Poor and Punish the Wrongdoer".

He said: "These words could equally be inscribed on this far more modest building, the Manukau District Court."

Mr N will be sentenced next month, and Judge Wade said he was considering home detention.