From Friday to Sunday of Easter 2026, the school will welcome old boys and girls, along with staff and faculty past and present.
"We’d like people to start getting their registrations in now at sohs100.nz," principal Mike Wright said.
"We’ve had interest from former students in Australia, America, the United Kingdom and beyond."
He said reminiscing and networking would be accompanied by tours of the recently refurbished campus, with a Saturday night live-music social in the gymnasium and gourmet buffet as the main event.
The Balclutha District High School Committee decided unanimously in 1922 that the region needed a full-status high school.
Four years later, South Otago High School opened for 135 pupils and five teachers backed new rector John Reed and the motto "by faith and fortitude".
District and school grew rapidly in the 1950s and 1960s, by the early 1970s twenty classrooms had been added with more than 40 teachers.
It was always co-educational — which was very unusual in 1926 — and is now one of the oldest schools in Otago, with 48 teachers and about 510 students today.
"Fourteen hundred people came to the 75th anniversary," centenary committee chairman Ken Blair said.
"Whether people have ventured overseas or stayed close to home, we’re hoping for even more next year."
