Some secondary teachers are calling for a review of the school zoning system because it is causing what they describe as educational apartheid.
The Waikato branch of the Post Primary Teachers Association (PPTA) says schools are increasingly polarised along ethnic and socio-economic lines.
In a paper to the union's conference in October, the branch said there was evidence some schools were abusing zoning and enrolment rules in order to deliberately exclude children from poor families.
It said weaknesses in the rules allowed schools in rich areas to grow at the expense of schools in poorer communities.
The paper said students should retain the absolute right to attend their nearest schools but the zoning system needed to be reviewed and improved.