Education Minister Hekia Parata has now included a change in a bill currently before select committee that will give the ministry a new power to put in place a zone.
The cases of King's and Mercury Bay were cited in an accompanying regulatory impact statement.
The ministry was concerned King's growth would cause overcrowding and pushed hard for action - threatening to appoint an LSM.
An agreement was eventually reached for a zone to be put in place for 2017, but brought forward to May last year after enrolments exceeded 1035.
After the proposed zone was circulated, Kaikorai Valley College board chair Mark Rogers wrote to King's to express concern for the future of secondary schooling in Dunedin.
Otago had for some time achieved strong academic results, and that was possible due to a willingness to work together amongst local schools, Rogers observed in the letter, among documents released under the Official Information Act.
"Unfortunately this approach has become more difficult over the past couple of years as we have fallen into a very aggressive model of marketing for students."
Rogers noted that King's had assured parents that a good proportion of out-of-zone students would still be accepted this year, and pointed to a recent news report that quoted the principal of Burnside High School in Christchurch as saying its decision to cut out-of-zone numbers was to maintain a sustainable network of schools across the city.
"Without a change in thinking and direction, the current secondary schooling model in Dunedin will be very difficult to maintain and as a consequence parental choice will become more limited."
At Mercury Bay Area School, the only school in Whitianga that also provides secondary education for the primary schools in the wider area, principal John Wright successfully objected to the ministry's case for a zone.
A memorandum of understanding was instead signed with nearby schools, who submitted they did not see the need for a zone.
David Booth, board chair at King's, told the Herald that its roll had steadily increased following strong academic results and Education Review Office reports, and the school believed parents had a right to school choice, particularly those that wanted a boys' school.
"The question back to the ministry is, why are you knocking the tall poppy and why do you not seek to provide more assistance to those schools that might need more support to improve their results?"
Allan Vester, chairman of the NZ Secondary Principals Council and head of Edgewater College in Pakuranga, said he supported the new zoning power for the ministry.
"Far more ministry oversight is needed to ensure that all schools act in a way that is best for all students and not be so narrowly focussed on the individual school."
The "communities of learning" (COL) system introduced under National, in which certain teachers and principals are paid to work across groups of schools, has building collaboration as a key goal.
"Over the next few years the level of success of COLs in turning around that 'each school is an island' model will show just how entrenched competition has become," Vester said.
