The Kohanga Reo movement plans to survey the first intake of Maori children, to prove to the Government that educational qualifications don't always mean success.
The Maori Affairs Department opened the first language nest centre, Pukeatua Te Kohanga Reo, in Wainuiomata, near Wellington in 1982.
In 1990 the Ministry of Education took over the responsibility, and imposed rules such as teachers needing to be qualified.
A Kohanga Reo National Trust Board member says the survey will ask former pupils how beneficial Kohanga Reo was for them.
Dame Iritana Tawhiwhirangi says there's a perception that unless children are in a model education system they won't achieve, but the trust wants to prove that's not the case.
The survey will start later this month.