Dame Tariana Turia has confirmed she has joined the claim before the Waitangi Tribunal, opposing the shutdown of Kura Hourua.
The Treaty claim, led by Sir Toby Curtis and Irirangi Tawhiwhirangi alleges closure of the schools would have a detrimental effect on Māori as Māori students make up the majority of the 1,500 students enrolled.
Curtis told the Education and Workforce Select Committee their failure to consult properly is in breach of the Treaty.
He believes the claim will enable Māori to be properly heard.
Turia says she has been a staunch supporter of Kura Hourua from day one.
"For as long as our whānau advocate for options for success for our tamariki mokopuna, I will be part of this fight," says Turia.