More than 400 people attended the reunion, which involved 13 schools that had served the district.
The occasion also marked the 75th jubilee of the Omakau School, which is the only one of the 13 schools which remains open.
Reunion chairman Ross Naylor said the jubilee was a good excuse to celebrate primary schooling in the district and bring together former pupils, teachers and others who had links with any of the 13 schools.
"The school is still the focal point of the community and we have every reason to celebrate," he said.
Mrs Richmond said the Omakau School roll had peaked at 84 in 2000, after Becks School amalgamated with Omakau.
At the end of last year, the roll was 50 pupils - "one short of the magic 51 that would allow us to have three teachers again, but we remain hopeful of regaining a third teacher".
Board chairman Ian Rietveld said the school was a major factor which influenced his family in shifting to Omakau 14 years ago.
"I think all our children have benefited from being in such a strong and supportive community, with an equally strong school."
The long-term goal was for the school to continue on, in the same vein, he said.
The weekend celebrations included two evening functions, a tree-planting in the school grounds, the unveiling of a plaque to mark Omakau's 75th anniversary and the burial of a time capsule, to be unearthed at the school's centennial.
The capsule included photographs of school events, examples of school work, a copy of the curriculum and strategic plan, several newspapers, the jubilee book and a school shirt.
Former pupils or staff from nine of the 13 schools which once served the district took part in the celebrations.
