Decile-based funding was introduced by a National Government in 1995 as a means of bridging the socio-economic advantage schools in wealthy neighbourhoods have over those in the poorer parts of town.
Broadly, the lower a school's decile - a rating based largely on household incomes in its district - the more money it is given on top of its per-pupil allocation. The aim was worthy even if the outcome has been patchy.
Now, however, the Secondary Principals Association wants the system reviewed, saying it has been responsible for "white flight" from low-decile schools.
Its call follows the release of Education Ministry figures that show only 30,000 Pakeha are attending deciles 1, 2 and 3 schools, half the number at such schools in 2000. This means only a fifth of the pupils in these schools are Pakeha, down from a third.
The ministry's interpretation of the statistics is much more benign than that of the association.
It points to population change, the creation of new schools, and movements in schools' decile ratings as their communities' wealth changes.
Either way, the principals' concerns are much overstated. In the past, some parents may have confused decile ranking with a school's academic achievement. But this concern has been allayed to a large degree by the publication of tables of examination results. These enable parents to gain a clearer picture of how a school is performing, most notably in relation to the average pass rates for its decile.
With the rider that some schools encourage pupils into alternative examination systems, if a school's NCEA results are lower than others in the same grading, parents will be wary of sending their children there, or keen to shift them to a school that is performing better.
The evidence of the tables published last year was that in all but a few categories, the decile funding was not enabling pupils to match those in schools ranking immediately above them, let alone their contemporaries in the wealthiest deciles 8, 9 and 10 schools. This suggested either that the extra money was too little or that it was not being used wisely.
But a few decile 1 schools did achieve results in NCEA that were equivalent to schools at deciles 6 and 7. Their success suggested that the funding, used astutely, could compensate for the advantages enjoyed by those who came from wealthier homes where educational success was more likely to be valued.
Still, however, the Secondary Principals Association suggests the achievements of some lower-decile schools will be unknown to many parents "because they simply see decile 1 and equate that unreasonably with poor academic achievement".
But most involved parents are surely keenly aware of how well a school is doing. Equally, schools, quite rightly, trumpet good exam results. It is highly unlikely that they will lose pupils. But if a school has not been able to make the most of its decile funding, parents wishing the best for their children will, obviously, strive to place them in a wealthier zone.
The principals do not want the funding provided by the decile system to be abandoned. But they say the "stigma" created by publishing decile rankings should be eliminated. That, as is often the case within the sector, exposes two failings. The first is the instinct to keep information out of the public eye.
The second is the unflattering light in which they often cast parents. Parents are deemed unable to distinguish between schools that provide an education that will give their children the opportunity to gain the best-possible qualification and those that are not providing the best for their pupils.
This understanding is most probably driving much of the movement to schools in richer neighbourhoods. As such, the principals should be applauding parents for their perspicacity, rather than reading dark things into their actions.