The Ministry of Education is being called on to investigate a US researcher's claim that most Auckland secondary schools intentionally skew enrolment zones to improve decile ratings.
Fulbright scholar Associate Professor Chris Lubienski looked at 49 secondary schools, comparing surrounding areas with the areas actually included within the zones the schools have drawn.
In 36 cases, Mr Lubienski said the enrolment zones do not match the surrounding population.
"What we found in vast majority of cases that the schools were serving students who were more affluent," he told Radio New Zealand this morning.
"It suggests that they were drawing school boundaries in a way to exclude students who were more deprived and tended to come from minority backgrounds.
"So it's a way for schools to protect and enhance their market position.
"In only 14 percent of all of the cases were schools drawing zones which were serving a more deprived cliental than in the surrounding areas."
The schools took part in the research on condition of anonymity.
Mr Lubienski, from the University of Illinois, said he can only infer there is intention from schools to distort their decile rating, although he said in the qualitative part of study principals did talk about intentionally drawing up zones to enhance their school's market position.
He told Radio New Zealand one principal even said she removed the names of undesirable students from the ballot for out-of-zone enrolments.
It comes after education leaders last week called for a review in the use of the decile system after figures revealed Pakeha parents were avoiding lower decile schools.
The Ministry responded to Morning Report in a statement, saying ministry guidelines state "householder income should not be considered when zones are drawn up".
"The law requires a board to ensure all students can attend a reasonably convenient school while ensuring other schools do not experience enrolment problems.
"If a school board is unable to agree a boundary arrangement the ministry can step in to resolve the matter. If necessary, the ministry has powers to require a board to amend a proposed enrolment zone."
Professor Lubienski's research was presented at the Secondary Principals' Council Conference in Hamilton last week by University of Waikato Professor Martin Thrupp.
Labour's education spokeswoman Nanaia Mahuta said school zoning should enable local students, no matter what their socio-economic background, to attend their local school.
"The Ministry of Education should ensure that all public schools work in the best interests of all students rather than allowing schools to screen out what they may determine as 'undesirable' students.
"If we want all learners to reach their full potential and contribute to a better society then our public school system can help achieve that by getting rid of 'stigmatising' attitudes,'' she said.
Allan Vester, Secondary Principals' Council chairman and principal of Edgewater College, said he wasn't surprised by the findings.
He said the Tomorrow's Schools model was adopted by the government in the 1980s because it believed the best way to improve education was for schools to compete.
"The system is incentivised basically for you to do that. You get enrolments wanting to come to your school, and enrolments wanting to come to your school if you're seen as having a really good reputation. Therefore the best way of making sure you've got a really good reputation is to have the very best students that you can.
"There is an incentive built into the system to include as many students who are as good as you can, and exclude as many as you can who won't add to your reputation. I think that's the whole nature of New Zealand schools,'' he said.
"The Ministry of Education do have more teeth now to stop them doing things that aren't fair, but under the previous governments, schools and boards of trustees had considerable power to set their zones,'' he said.
Secondary Principals' Association head Patrick Walsh said the allegations, if true, were very serious and the Ministry of Education would need to look at them seriously.
He said the competition between schools was ramped up, particularly in light of a proposal to introduce league tables.
The Green Party called for a review of the Tomorrow's Schools model in light of the research.
Education spokeswoman Catherine Delahunty said the party had long advocated for a review of the model she said put schools in competition with one another.