The "unlawful" decision to merge a Christchurch school will see 70 per cent of its pupils "scatter" to other city schools, a court heard today.

Phillipstown School has launched a High Court legal battle against Education Minister Hekia Parata's decision to close it and merge with nearby Woolston School to create a 465-child super-school next January.

The merger came as part of the Government's $1 billion shake-up of post-quake Christchurch schools.

The ministry said the school suffered quake damage and it made sense to merge its small roll of 163 with another small roll.


But the decision caused mass upset with the decile 1 school's pupils, teachers, and the community.

The school has launched a bid for a judicial review at the High Court in Christchurch today, with around 50 parents, children, and community leaders packing into the public gallery on the first day of school holidays.

The school has employed counsel Mai Chen, who last year successfully got a High Court judge to overturn the Government's decision to close Salisbury School, which was deemed unlawful.

This morning, she argued that it was not a closure decision, but a merger decision, and one that Ms Parata failed to meet the pre-conditions under the Education Act 1989.

The minister also made the flawed decision in the "extraordinary and unprecedented context" created by the earthquakes, Ms Chen said.

The process was flawed and essential information, including geotechnical reports and detail on strengthening of buildings, was not made unavailable to school before the decision was made, or it was misleading or missing.

Ms Chen said that during consultation, the ministry did not provide the school with enough information despite parents telling them they still didn't understand "why Phillipstown School?".

A judicial review must be heard "urgently", given that after October 29 "irrevocable steps will be taken to implement the closure" of the school, Ms Chen said.

The school's legal team had presented evidence that "makes it clear" that only 30 per cent of pupils will transfer to Woolston, while the other 70 per cent will "scatter" to other schools throughout the city.

It's going to have a "significant impact" on the community, which is "economically poor" and "deprived in many ways", Ms Chen said.

Principal Tony Simpson, who before court this morning said it was "a sad day", gave a written affidavit that said the decision "severely threatens to tear apart the social and cultural fabric" of the community.

If Justice John Fogarty rules in favour of the school, Ms Parata's decision should be quashed, so she can undertake consultation again "with an open mind", Ms Chen said.

The case, which is set down for two days, continues.