The 97-year-old said the 1918 epidemic was her earliest memory of the school, which celebrated its 150th anniversary this weekend.
"I remember having to gargle Condy's crystals [potassium permanganate], and ruining my new frocks with it."
As the oldest former pupil attending the reunion, Mrs Grubb, who still lives in the town, was asked to cut a cake to celebrate the occasion along with new school pupil Ryleigh McAra (5).
Mrs Grubb said the current school was a much more social place, where children were encouraged to be themselves.
"Our teachers were so very strict."
School principal Trudy Pankhurst said the 91 school pupils had been learning about what it would have been like to be at school 150 years ago, and had concluded they preferred the modern version.
While many features of school life were similar, teaching styles had changed to provide more stimulating lessons and cater for different learning styles, she said.
One of the earliest public schools in Otago, the school was opened in October 1860 after the Beach St land was given by prominent settler Johnny Jones.
The school moved to its present site on Malloch St in 1870.
More than 200 people attended the reunion events over the weekend, beginning with an informal catch-up at the East Otago Events Centre before the formal opening, photographs, dinner and dance on Saturday.
The reunion concluded with a church service and then a fair at the school yesterday.
