Jubilee committee chairman Nigel McLachlan said much had changed since the school's 50th jubilee in 1989.
In December 2007, the old Clutha Valley School was demolished.
The present school was built the following year.
''While it was sad to see the old school go, the new school secures the future.''
Principal Val Ward said the school's pupils came from 10 different nationalities as dairy farming had increased in the area, bringing people with a wider range of backgrounds.
Gwen Treacy (91), an ex-pupil of the former Awamangu School, and youngest Clutha Valley Primary School pupil Toby Allan (5) cut a cake marking the milestone.
The cake-cutting was followed by the unveiling of a commemorative plaque, photos and afternoon tea.
About 270 people attended a dinner at the Balclutha War Memorial Hall on Saturday night, and celebrations wrapped up with a family picnic at the school yesterday.
A total of 367 people registered for the event.
Clutha Valley School opened as a district high school on February 1, 1939, with 154 pupils, following the merging of eight schools - Awamangu, Clydevale, Greenfield, Popotunoa, Pukepito, Puketi, Waitahuna West and Wharetoa.
They were joined by Taumata School in 1946 and Tuapeka Mouth School in 1949.
The secondary school closed in 1967, leaving students to travel to South Otago High School in Balclutha.
The school, now Clutha Valley Primary School, has a roll of 92 pupils from new entrants to year 8, with five fulltime teachers and three teacher aides.
