Education regulators designed school zoning for the sake of equality. If all children in every locality were to attend their local school, they reasoned, all schools would have roughly the same range of abilities among the pupils and no state school would face undue competition.
It has not worked, as plenty of urban schools with declining rolls can attest. But if any Government proposed to abolish zoning today there would be an outcry from homeowners within zones drawn for prestigious schools.
Yesterday we reported that median house prices in Auckland's "Grammar zone" passed $2 million last year, double the median price 10 years before.
The arbitrary line that schools such as Auckland Grammar and Epsom Girls Grammar have been obliged to draw around themselves has created substantial wealth for those fortunate enough to have a house within it, and fierce resistance to any variation at the margins.
When a neighbouring school drew a zone that slightly overlapped the Grammar zone a few years ago it householders in the overlap consulted lawyers for fear the Grammar zone could be reduced.
Prestigious schools do not particularly want their zones. The previous principal of Auckland Grammar, John Morris, frequently complained about the ruses parents used to make it appear they lived in the zone, and the resources the school had to commit to checking where pupils really lived.
Zoning has not even achieved the minimal educational purpose of keeping enrolments within the capacity of schools in demand.
The schools are obliged to accept the children of all who can afford to move into the zone and our report yesterday described the sacrifices some parents are making in order to afford it.
The alternative to zoning for schools in demand is to allow them to draw up a set of criteria for selection of pupils from anywhere.
But that would mean schools would be able to choose their pupils, which is an even greater anathema to education theorists than parents being able to choose their child's school.
In theory it could also create an injustice if pupils living very close to the school were not selected and had to travel some distance to another. That was the argument advanced by National voters in Epsom for the restoration of zoning in the 1990s.
But the problem was more apparent than real. Proximity would be one of the criteria a school's selection policy would take into account, though it would not be definite enough to provide a real estate premium.
In the name of equality, education policy makers are maintaining a system that gives access to the most desired schools on the basis of the ability to afford the property values their zoning has created.
They deny the same opportunity to less well off children of high potential who could gain selection if it were permitted.
These children are not all attending their nearest school, parents are sending them wherever they think the child might do better.
Education should open doors for everyone to fulfil their potential. When it attempts to enforce educational equality the consequences can be as perverse as Grammar zones.