The Public Service Association says it is worried Education Minister Ann Tolley is considering closing one of only three special residential schools for young people with severe behavioural problems.
Radio New Zealand has obtained a letter from the minister to Waimokoia School's current commissioner Dennis Finn which says she is considering the future of the school.
In the letter, Mrs Tolley says Waimokoia School in Auckland is not currently offering a balanced and quality education setting for its 44 students.
A 2005 ERO report identified a number of concerns about the school's operation in health and safety, staff management, learning and teaching, and governance and management.
For example, students were isolated by being placed in 'time out' in a small concrete block shed.
But a 2006 ERO review says the commissioner and directors of the school had made progress in addressing many of the specific concerns and the more extreme isolating strategies had been almost completely eliminated.
The PSA union represents some of the staff at the school.
National secretary Brenda Pilott says there have been difficulties at Waimokoia School in the past, but staff say there has been a recent turnaround under new management.
Mr Pilott says there is a severe risk to the young people, their families and their community if the school is closed.
However, Mrs Tolley says the advice she is considering is based on a 2008 ERO review commissioned by the ministry, It noted that the school has had a lengthy history of governance and management difficulties, with a commissioner in place for the past nine years.
The minister says it is important to consider the longer term best interests of the children at the school.
Commissioner Dennis Finn says Waimokoia School has made a recent turn-around and there is no doubt it has been improving. He says his submission on the school's future will be based on consultation with staff and the community.