Te Kohanga Reo National Trust expects supporters from throughout the country to be in Wellington on Monday to hear an urgent claim before the Waitangi Tribunal.
The tribunal granted the trust a hearing in October last year, following a Ministry of Education report which was critical of the kohanga movement.
The trust claims the Crown has treated kohanga reo like an early childhood education provider, which undermines its kaupapa and contributes to what it calls the perilous state of te reo.
The trust is seeking protection under the Treaty of Waitangi.
Co-chairperson Tina Olsen-Ratana expects many supporters to attend the inquiry, because every whanau is likely in one way or another to have had some kind of role in kohanga.
The inquiry runs until 23 March.