The St. Trinian's girls burn down the school building, go on trial at the Old Bailey, and are found guilty. Professor of Philosophy Canford of the University of Baghdad suggests that, rather than punishment, the girls need sympathy. He offers funds for a new school building, where with the help of noted educator Matilda Harker-Packer, the girls can be rehabilitated.
To demonstrate the positive effects the sympathetic educational approach is having on the girls Harker-Packer suggests the school present a cultural festival featuring a fashion show, a painting demonstration, and a dramatic presentation. Ministry officials Culpepper Brown and Butters are invited. The show is a fiasco. Certain the Minister will close the school when they present their report, Culpepper Brown, Butters and Blackwood are crushed when the Minister explains that the fashions are due to be shown in London, a reputable gallery will exhibit the art, and the Stratford theatre will present the girls' Hamlet.
Canford suggests that he take the sixth-form girls on a cultural tour of the Greek Islands, however after a series of misadventures they end up on an island in the East Arabian Sea. They are rescued and transferred to an army base in the nearest town, Makrab. The girls take over the base but a fight ensues. Things look bleak, when they hear the St. Trinian's school song in the distance, followed by the arrival of the fourth-form girls in army vehicles, who smash their way into the compound.
The Monthly Film Bulletin wrote: "The Pure Hell of St. Trinian's demonstrates that reputable producers are just as capable of turning out third-rate British farces as any mushroom growth B-picture studio. Given a script without a vestige of originality, Frank Launder's capacity as a director is revealed as correspondingly tired and easily satisfied; his film, despite a promising opening, could hardly be more shapeless or laborious. The experienced actors give embarrassing performances, and the monstrous girls themselves, uprooted from their proper environment, are left like their elders to cope as well as they can against a series of arbitrary backdrops – army encampments, desert islands, Arab market-places, that sort of thing."[3]
Time Out regretted that "inspiration seems to have deserted the St Trinian's scriptwriters," but noted "Some bright moments."[5]
The Radio Times Guide to Films gave the film 2/5 stars, writing: "Bereft of Alastair Sim, the third film in the St Trinian's series ... has its moments, but sadly all too few of them. With the school reduced to smouldering ashes, mysterious child psychologist Cecil Parker takes charge of the tearaways, in league with white-slaving sea captain Sidney James. Woefully short on mayhem, the film spends too much time in the company of eventual castaways Parker and Joyce Grenfell."[6]
