The closure of Nelson's Salisbury School, attended by 11 Waikato girls, could be stalled if the board takes legal action.

But Education Minister Hekia Parata says the ministry went through a robust, six-month process before making the final decision on Wednesday to shut the special school.

Salisbury, along with McKenzie Residential School in Christchurch, will be closed in January.

Students from these schools have the option of enrolling at Halswell Residential College in Christchurch or Auckland's Westbridge Residential School.

There will be an expanded "wrap-around" service for children elsewhere in New Zealand, including about 11 girls from Waikato.

However, Cambridge lawyer and Salisbury board member Jocelyn Cooney said the school was considering legal action.

"Obviously we're all really disappointed, but from a legal point of view I think they've made a complete cock-up."

Section 146(A) 2 of the Education Act 1989 meant Halswell could not legally become a co-educational school before January 2014, she said.

"It would therefore be unlawful for [Ms Parata] to close Salisbury for 2013."

A legal challenge would allow a year for the school to fight to remain open, or for the ministry to prove that the alternative was sufficient.

"It will give the ministry a chance to prove to us, and to parents, that the wraparound service is in fact effective. Because right now they're not showing us anything."

However, in a series of emails between Salisbury's lawyer, Mai Chen, and the Education Ministry's group manager for special education, Brian Coffey, Mr Coffey defended the closure. "Prior to Halswell . . . becoming co-educational in 2014, the minister will, for the 2013 school year, limit the number of girls who can be enrolled at the school.

"She will, in doing this, have regard to the necessity of safeguarding the single-sex nature of Halswell for 2013."

Mrs Cooney said the ministry was "playing with words" by saying that Halswell could remain single-sex with only a limited number of girls at the school. There were also concerns about the risks of sending the girls to a co-educational school, where the students have teenage bodies, but the mental ages of about 5.

Ms Parata said deciding to close the schools had been difficult, and she was not aware of any potential legal challenge. "That never precludes the possibility that the school undertake a judicial review."

- © Fairfax NZ News