The board of Phillipstown Primary School in Christchurch has filed papers in the High Court seeking a judicial review of a decision to close it.
The school is seeking a declaration that the Government's decision to close and merge it with Woolston School from the beginning of 2014 is in breach of the Education Act.
The board of trustees says it is sad to be taking legal action but it is the only option left.
Chairman Wayne West on Monday the school needs an urgent hearing, because if it waits any longer there will be no school to save.
Mr West said the closure decision appears to be based on factual mistakes and believed there was insufficient consultation.