The Law Society says a proposed law change on school zoning that would give priority to children of former pupils is unjustified and discriminatory.
The society on Wednesday presented its submission on the Education Amendment Bill to Parliament's Education and Science Committee.
It asked the committee to remove the provision that would give preference to former students of state schools.
Kristina Muller of the Law Society says when it comes to competing for a limited public resource, it is difficult to see why children of past students should be given preference.
"The right to freedom from discrimination based on family status is guaranteed by the Bill of Rights Act and we feel that if that right's going to be diminished in any way, there should be grounds shown for doing so and we haven't seen an argument made in this case."
Ms Muller says there is some argument for private schools to discriminate based on family status because they rely more on parental support.
The headmaster of Auckland Grammar School, John Morris, says the school wants to keep inter-generational links going and old boys who live outside the zone would love their sons to attend the school.
He says the proposed law change would benefit all schools, as the ideal of a family and community school is paramount in New Zealand culture.
Mr Morris says the other positive for his school is that will allow it to reconnect with Maori and Polynesian families.
Before the zoning rules came in Maori and Polynesian students made up 7% of the roll, but that has now fallen to 2%, he says.