Two co-educational secondary schools in Dunedin plan to cut teacher numbers as the fall in school-age children starts to affect the secondary sector.
The March roll return shows secondary school rolls in the city have dropped by 612 in the past decade - the equivalent of about 25 large classrooms of pupils.
Kaikorai Valley College principal Rick Geerlofs said it was a situation affecting many Dunedin secondary schools.
"It's fair to say that the number of students for secondary schooling is declining across the city.
"Our year 9 roll intake is very positive and up on last year.
However, we do have some big cohorts on the top end of the roll moving through, which is affecting the school roll."
As a result, the school was not in a position to employ new staff, and staff members who were resigning and retiring were not being replaced, he said.
"It is staff management through attrition.
"We are exploring new ways of managing the impact of falling rolls."
He expected next year's roll to be "in the early 500s", including a significant number of international pupils.
The school this year posted its lowest March roll return in a decade, at 595.
Bayfield High School principal Judith Forbes said year 9 enrolments were similar to last year, but a large cohort of senior pupils leaving the school at the end of this year meant the school's overall roll would drop by about 20 in 2013.
The school posted a March roll return this year of 624. .
Both Mrs Forbes and Mr Geerlofs said staff numbers would have to be cut, but it was too early to say how many would go.
Mrs Forbes said she too was hoping to resolve the problem of excess teaching staff through attrition.
"It won't be a large number. We've got some staff retiring at the end of the year and we're hoping that will cover it."
Taieri College acting principal Paul Bolton said it was a situation his school was also wary of.
"Our roll is stable enough to not have to go through that process yet, but it's something we are having to keep a very close eye on from year to year."
The school's roll was at just over 1000, and it was expected to remain that way next year, he said.
Queen's High School principal Julie Anderson said the school's roll had been in decline, but was now "stabilised", so no further managing of staff had been necessary.
However, she said attrition was used by the school three years ago to manage staffing levels when the school's roll dropped below 500.
Logan Park High School deputy principal Roger Tobin said the school was expecting an increase in the number of year 9 pupils next year, and the overall school roll would increase by nearly 40.
"We're optimistic about being up on year 13 pupils next year as well." Secondary schools in rural Otago do not appear to be as significantly affected by roll fluctuations. March roll returns for the past decade show rural secondary school roles have remained stable, and those that have declined have been minimal compared with some Dunedin schools where rolls have dropped by up to 50 a year for the past five years.
Some rolls in Dunedin have nearly halved in the past decade.
Earlier this year, Statistics New Zealand senior demographer Kim Dunstan said the roll decline, particularly in Dunedin, was caused by a drop in the birth rate which began in the early 1990s.
He said there were 1700 births a year on average in Dunedin around 1992, but the number had fallen to, and plateaued at, about 1300 a year since 2000.
