The Ministry of Education says a Christchurch intermediate's roll is being reduced to encourage students to go to their local school.
Chisnallwood Intermediate was told last month the ministry was pushing ahead with plans to cut 200 students from its roll by 2025.
As Education Minister, Chris Hipkins asked advisers to justify why the 400-student roll cap had been chosen last year.
A document answering his query said 75 percent of the intermediate's 2021 roll were out-of-zone students.
The document said: "Several schools near Chisnallwood Intermediate have engaged with the ministry in recent years regarding the large number of out-of-zone students enrolled by Chisnallwood, and the impact this has on their own school roll.
"A build capacity of 400 would result in the number of out-of-zone enrolments to reduce by half."
It also advised changing the school's zone "so it better reflects the current design of the local network of schools".
Chisnallwood's zone was established in 2005 and sections of it had since been redzoned following the Canterbury earthquakes.
"Providing capacity of 400 at Chisnallwood Intermediate would be less than the school's pre-earthquake roll capacity, but would still provide more capacity than required to meet local demand and retain an out-of-zone roll of around 230 [students] based on current enrolment patterns," the document said.
It was one of the last two schools still yet to enter the Christchurch School Rebuild programme.
The ministry also noted it had planned for roll expansion at three of the city's other intermediates, Casebrook, Heaton and Shirley.
Shirley Intermediate was just four kilometres away from Chisnallwood and had a roll of around 150 students, despite a capacity of 400.
"A low share of local students attend Shirley Intermediate. A large proportion of these [local] students have been accessing Year 7 and 8 education at Chisnallwood Intermediate," the document advised.
Ninety-six Shirley-zoned students attended the school, while 61 went to Chisnallwood in 2021.
Chisnallwood principal Justin Fields said the school was not giving up and was considering its next steps.