The dominance of Wanganui's largest secondary school is set to be mitigated by its new principal's hard line on out-of-zone enrolments.
Garry Olver, who took up his post last month, said refusing to consider applications from potential students who lived outside Wanganui High School's enrolment zone was "the right thing to do".
The school's roll of 1739 includes 70 international students.
Mr Olver said he was not opposed to further growth in student numbers, but not at the expense of other Wanganui secondary schools.
The move will mean at least 30 students who have applied to attend Wanganui High School (WHS) next year will be turned away, because they live outside the school's enrolment zone.
Mr Olver said the policy ensured WHS would not be poaching potential students of other secondary schools in Wanganui.
The enrolment scheme does provide places for those who are siblings of current or former students, and for those whose parents are former students, employed at the school or on the board of trustees, regardless of where they live.
But the ballot that operated for all other applicants has been scrapped.
WHS's waiting list is also no longer open to those outside the enrolment zone.
Community leaders urged action on a glaring imbalance in Wanganui secondary school populations last month.
A spokesperson for the Ministry of Education yesterday confirmed WHS had the right to refuse out-of-zone enrolments.
Mr Olver said WHS's roll was set to decrease next year, but that was the result of a lull in the number of potential Year 9 students living in Wanganui.
The roll would be down about 50 Year 9 students in 2013.
Mr Olver said that would have a significant flow-on effect, but the school had managed to avoid redundancies through the voluntary departure of seven staff members.