But photographers hoping for the flour-throwing antics of the film schoolgirls, were disappointed. The role models for the hit comedies of the Fifties and Sixties are refined septuagenarians with mixed feelings about their notoriety.
"There was a big rumpus when all that came out and we all felt the films desecrated our school," Yvonne Macleod, 78, said. "Our headmistress, Miss Lee, stood up and told the school `After 20 years at St Trinneans, I am broken-hearted'."
But Joan Campbell, 75, who organised the reunion in Edinburgh, the first for 13 years, said the girls had "no complaints at all" about the films. "In fact, it was great to be known as the girls from St Trinneans."
St Trinneans School for young ladies and boys up to age 10 opened in Edinburgh in 1922. Under headmistress Catherine Fraser Lee, it became famous for radical educational techniques. Pupils danced to music on the school's manicured lawns while memorising facts and figures.
For an entire term, Miss Fraser Lee insisted pupils ate meals in reverse order, starting with pudding and finishing with soup. Dr Campbell joined the school in 1928 so missed the meals experiment, but remembered dancing on the lawns on sunny days. "It was all great fun."
Fun, but not quite the mayhem portrayed in Ronald Searle's cartoons and the later films in which girls drank hooch, gambled and plotted to blow up the school. Miss Lee became the sorely tried Millicent Fritton, played by Alastair Sim, and the films also featured a youthful George Cole and Joyce Grenfell.
Searle first heard of the school from a friend and former pupil, the artist Cecile Johnston, in 1941 when stationed as a soldier in Kirkudbright. St Trinneans - Searle changed the spelling - moved at the outbreak of war to Galashiels in the Borders and closed in 1946.
Disappointingly, the real St Trinnean's was just a genteel school for the middle classes and there never were any black stockings. The girls wore Harris Tweed coats with pale blue tunics, and the stockings were fawn.
Nearly 100 old girls turned up for what is expected to be their last get-together. "It's now or never," said Pat Hendry, 75. They came from as far afield as the USA and South Africa, but mostly Scotland.
The original Gothic-style school building, adorned with turrets and battlements is now the centrepiece of Edinburgh University halls of residence.
And if food was pelted about during lunch, it was away from the media's prying gaze. Insisting on privacy, Dr Campbell - a former head girl - laid a firm hand on the arm of one reporter with the instruction: "That's your lot, my dear, out you go."
Joyce Grenfell could not have done it better.Reuse content