But he told the Herald intensification meant action was needed.
That could be major investment in classrooms and property, new schools or changing the law to let schools tighten the rules.
Mr Seymour floated the idea of removing the automatic right to attend local schools from residents in yet-to-be-built apartment or housing developments.
"I just look at the advertising that surrounds a lot of these new developments. It used to be 'location, location, location'. Now it's 'Grammar zone, Grammar zone, Grammar zone'."
Another possibility was letting schools crack down on certain cases where a student lived within zone but without their parents.
Mr Seymour said schools had told him of cases where a property would be bought, but once permanent residency was granted the parents would live overseas, and eventually sell after graduation for big capital gains.
During schooling the child would remain at the property with relatives or family acquaintances, and this could cause pastoral care issues for the school.
"If you purchase a property, and then leave the country, should [your child] still be entitled to a state education in New Zealand when you may not be making a contribution as a taxpayer? I think that is a question that should be asked," Mr Seymour said.
'Communist-style Russia'
EGGS principal Lorraine Pound said the board had concerns relating to the Unitary Plan and possible intensification effects on the roll. "We would welcome meeting with the Ministry about this issue and the best ways to deal with it."
Auckland Grammar headmaster Tim O'Connor said the school could in the future make a submission on enrolment rules as set out in education legislation, but he did not want to comment presently.
The school has a fulltime enrolment registrar and requires parents to hand over documentation to prove residency. A private investigator has at times been used to door-knock properties to check students were living in zone.
Ms Parata last night said: "Roll-growth pressure in parts of Auckland is the subject of an ongoing conversation between schools, the Ministry, the associate minister of education Nikki Kaye and me." She had spoken with Mr Seymour about the issue and heard his suggestions, and expected to discuss them further.
However, property developers believe such a change would be unfair and that schools should instead look at expanding.
John Harman a Remuera breast surgeon building an intensive residential scheme on a St Mark's Rd site, said of Seymour's suggestion: "It's like something out of communist-style Russia.
"The schools should be developed more to take more students. They must build up. You look at the investment going into private schools in the area," he said citing upgrades and extensive building work at Diocesan School for Girls and others.
Auckland Grammar School has already expanded with a new $6.4 million 12-room classroom project on its site. That development has three teacher resource rooms and a tuckshop, built adjacent to the school's historic main block.
Watts & Hughes Construction was the main contractor on the project designed by Architectus.
The Herald reported two years ago how the Ministry of Education funded about a third of the total building cost so the school had embarked on a $4 million fund-raising project under way, the biggest in its history.
Coping with demand
Changing a school's zone is one tool used by the Education Ministry to help schools cope with demand for places.
In 2014 One Tree Hill College and Selwyn College backed down from plans to have proposed zones overlap those of Grammar and EGGS.
Residents were assured they could choose which school their child attended, but some believed it might be a first step to their eventual exclusion from the "double grammar zone" and a corresponding loss in property values.
Mr Seymour started a petition against the proposed overlap, and local resident and lobbyist Matthew Hooton and other residents briefed law firm Russell McVeagh.
New schools can also face resistance. The ministry paid $7.5 million to the Auckland Trotting Club for more than 3ha of Epsom land in 1999 for a 1500-student school.
The school never eventuated after fierce opposition by residents who wanted to stay in-zone for existing schools.
