Children's Commissioner John Angus has criticised the treatment of children in foster care and Child, Youth and Family homes.
In a report released on Thursday, Mr Angus says children are moved between homes too much, causing huge disruption to their schooling.
Some children quoted in the report say they have been at too many schools to count and feel stigmatised because they are living in care. Mr Angus says the report also found children did not feel engaged enough in planning their future.
Many of the children quoted in the report want more contact with their birth families.
Some foster carers say that access visits are not always handled well by agencies, and that, in some cases, older children return after being allowed to take drugs, drink alcohol and watch pornography.
The deputy chief executive of Child, Youth and Family, Ray Smith, says he would be surprised if that were able to happen on a supervised visit.
Mr Smith says a government initiative launched last month will encourage permanent foster placements for children.
Mr Angus says the bar needs to be set higher for services provided by Child, Youth and Family to children in foster care. The agency, he says, is not getting a good assessment of the children's health and education needs.
More inter-ministry co-operation urged
The Family and Foster Care Federation says the health, education and social development ministries need to work together in the care of foster children.
The federation's chief executive, Iris Clanachan, says 51% of foster children are Maori and it is not always possible to place them into care within their whanau.
Ms Clanachan agrees with the report that foster children need to remain in contact with their birth families and says social workers need to advocate for that contact to be maintained.