A Ministry of Education report said Otago was predicted to be the second-worst-hit region in a nationwide shortage of high school teachers.
The region has 1339 teachers now and in the most likely scenario this year’s shortage of 60 teachers would grow to 90 by 2027.
In a worse-case scenario the shortfall could balloon over that period to 150.
Otago Secondary Principals Association chairwoman Jackie Barron said the statistics were "a bit frightening".
She said there were not many graduates coming through and schools had had to think outside of the box to fill positions.
They worked hard to bring in teachers from overseas and had encouraged staff who had switched to part-time status to return to full-time teaching.
She put some of the teacher shortage issue down to high demand for new teachers in Central Otago and Queenstown where there had been an influx of migrants.
There was no short-term solution to the problem but schools would do their utmost to ensure students were not disadvantaged by the shortage.
Otago Boys’ High School rector Richard Hall said it was getting harder to hire new staff.
"It’s deeply concerning to have Otago, a fantastic region for education, struggling to have teachers."
In particular, subject-specific teachers for maths, physics, chemistry and commerce were difficult to come by.
Over the past five years there had been an increasing number of overseas applicants.
Mr Hall said while they were often good applicants, integrating them into the New Zealand school culture and the city required more work.
"That’s a lot of extra work placed on schools and school leaders.
"I have to be involved in a lot more of their lives initially, and certainly to settle them."
He said the teacher shortage was a long-standing issue that no government had addressed properly.
Although a lot of teachers were being trained in Dunedin, many were being snapped up by North Island principals.
Mr Hall said some schools in Auckland had moved away from the university model and started training teachers on site.
The "apprentice model" could be the way forward for Otago schools, he said.
South Otago principal Mike Wright said it would be increasingly difficult to find New Zealand-trained teachers.
If the number of applications continued to decline, schools would struggle to provide a high-quality education.
The ministry had previously failed to forecast teacher shortages for 2024 and 2025 due to an error.
In a forecast published at the end of 2023, it predicted a surplus of teachers in all sectors.
The 2023 forecast failed to account for non-contact time changes that began last year.
