Social Development Minister Paula Bennett wants answers after social workers took four months to remove a wheelchair-bound boy from his home following allegations he was was being beaten, burned with cigarettes and starved.

Bennett has called for the agency to report to her on the case, in which the then 8-year-old boy's teacher and principal reported bruising, drastic weight loss and what appeared to be cigarette burns.

But help came only after the principal approached Manukau councillor and health board member Colleen Brown. Police and Child Youth and Family responded after she went to police commander Alan Shearer.

The mother faces a charge of assault and will appear in the Manukau District Court on Wednesday. The boy is with another family, although two of his siblings are with the mother.

Brown said it was "appalling" her contact with Shearer made a difference. "It does concern me that it's 'who you know'. The system should be responding to obvious concerns and needs of very young and vulnerable people."

The Herald on Sunday agreed not to identify the boy the principal and teacher had struggled to help, or the school he attended.

"Child Youth and Family failed to do their job," said the principal who says the saga brought him to tears. "They've since apologised."

The boy's teacher, who is also a trained nurse, said the boy's injuries and maltreatment were obvious. He was bruised, had blood in his urine and what appeared to be cigarette burns on his feet - an impression a police officer later confirmed to her.

She was appalled police took seven months to take a formal statement from her - they did so last month, after being contacted in November. She dealt with at least six CYF workers. "I wanted to scream at these people it was so frustrating."

The teacher said CYF workers had commented "poor mum she's not coping". "I said, 'Never mind the family. Protect that child."'

CYF twice promised to intervene but turned up late and sent the boy home, she said. When the third major abuse incident occurred the principal called Brown, who went to the police.

Detective Sergeant Ian McGill said he could not comment on the case. But he said in general child neglect was on the "end of the spectrum" compared with homicides and rapes which were top priority.

"[But] all child abuse is bad and all dealt with seriously... and we've done our best to put her in jail."

The teacher and principal said the mother had always denied causing the boy's injuries.

The teacher became concerned about the boy two years ago, after the mother missed medical appointments for her wheelchair-bound son, who could become partially mobile with surgery. The school wanted him to have this opportunity.

In July 2008 he had a split lip and claimed "mum did it". His moods changed and the school feared he was being neglected and starved.

In August, a truancy officer visited his home and found him home alone after he failed to turn up to school.

In September, bruising was found on his left shoulder and ribs and the boy started appearing increasingly upset. The school found bruising and swelling around his genital area and he had blood-stained urine. Fears grew when the previously overweight boy lost around 25kg in a short period.

The teacher claims the boy told her he sometimes was not given dinner or breakfast and was arriving at school teary, tired "and even lifting a pencil took great effort".

"We would give him food and it was horrible to watch. He was ravenous and pushed it all into his mouth at once," she said.

In October, he came to school with a bruised lip and cheek, blood in his ear and complaining of sore feet. The teacher found sores, which she says a police officer who later saw photographs believed to be cigarette burns."As soon as I saw it I thought 'oh my God'. I had to walk away. I got really emotional."

In November last year Brown contacted police. The principal praised officers "for getting the boy out of the house".

The mother, who was yesterday at home with a toddler, refused to comment on the allegations.

A CYF spokesman said the apparent burns were pressure points from callipers. But the teacher said the boy had plastic and foam splints, not callipers, to support his legs and feet.

Child, Youth and Family northern director Marion Heeney said the agency had worked closely with the family and other agencies to ensure they received the right support.

It checked on the family in 2006 after the boy missed two medical appointments and then again in September last year, finding no "care and protection concerns".

Police contacted CYF last November and the boy was then placed in fulltime care with specialist carers. "It became evident that it was very difficult to care for him at home."

A CYF spokesman said the boy had never been in the agency's care, however it had been working to get the family the best support available.

A spokesman for Police Minister Judith Collins refused to comment on the case.