Be afraid... be very afraid because the girls of St. Trinian's private school have returned for the new term, and they are notorious for being the most badly behaved in the whole country. The headmistress Miss Fritton (Alastair Sim) is none too bothered, because she has long learned to tolerate and indulge her charges in their mischief, and besides what is really concerning her now is the lack of funds the establishment is suffering. When a wealthy sheik sends his daughter to the school, however, things are looking up - until Fritton's brother Clarence (Sim again) gets wind of it.
The first of the St. Trinian's movies was a sensation on its release, and for Sim, whose popularity with the public new no bounds, it was a career high as he played not one but two dodgy characters, and one of those in drag as a most unlikely woman, which was part of the joke, naturally. It was also a highlight for the production team of Frank Launder (who also directed) and Sidney Gilliat, who had been alerted to the following Ronald Searle's naughty schoolgirl cartoons had among the young by their own offspring, and thought it would make a good premise for a film; in fact it became a whole lucrative franchise for them.
The premise of Searle's drawings was that anarchy and chaos were preferable to order and decorum, something that appealed to fifties kids who wished to be able to rebel against an education system far stricter then than it is now - there's no hint the pupils here would ever get the cane for their antics, for instance. Yet oddly when Launder and Gilliat translated those cartoons to screen form they opted not to make this a movie centered upon the kids, and instead gave the lion's share of the time to the teachers, leaving the girls a rather anonymous band of troublemakers, though once the plot involving a racehorse got going some of them won a decent amount of lines.
But really it was Sim who most would recall, and it's his comic talents which have made this endure in Britain as a longstanding favourite of irreverent humour, the sort of thing the nation's funnymen and women did so well. With a pleasing hint of off-colour japery ("I cannot afford to have continual arson about in my school!" quoth Miss Fritton - say it out loud), the results were a neat mix of broad gags such as the hockey match which descends into predictable violence, and more witty, character-based material at which this cast were only too capable. They included Sim's onetime protégé George Cole as Flash Harry, the role which surely put him in mind for Arthur Daley later on in TV hit Minder.
In addition, Joyce Grenfell appeared as the undercover policewoman, reuniting with Sim after their previous, not dissimilar success in The Happiest Days of Your Life, here in the film most would remember her for, and the teachers included such valuable character actresses as Beryl Reid (with a monocle), Irene Handl (teaching English with broad Cockney tones) and Joan Sims (very glamorous for a change). Even the pupils had a few recognisable faces amongst them such as Barbara Windsor or Shirley Eaton, and if you were very sharp you'd spot Searle himself as a parent. If this wasn't quite as consistently hilarious as its reputation, the overall sense of a bunch of professionals depicting a shower of non-professionals was very welcome, and there were many amusing lines which hit their targets, not to mention the clever sight gags (the school motto was "In Flagrante Delicto"!), so if it had a ramshackle air then that was by canny design. It's so cheerily badly behaved you can understand why so many took it to their hearts. Music, including the plinky-plonky theme, by Malcolm Arnold.