The presence of George Cole as the familiar “Flash Harry” doesn’t prevent the earlier Sim/Grenfell films’ flair and playful nature from being overshadowed by a more obvious style of humor, relying on suggestive jokes and broader performances from Frankie Howerd and Dora Bryan. Raymond Huntley portrays "Sir Horace," the government official who authorizes £85,000 to support the school and modernize it. However, the headmistress, “Amber” (Bryan), is his secret affair, and she redirects the funds to transform the school into a modern gambling den resembling something you’d find in Atlantic City. What they don't realize is that the old building housing the school was previously used by train robbers who are seeking their stolen money hidden beneath the floorboards. When the students discover this scheme, chaotic events unfold! Bryan and Howerd do generate some amusing moments together and show a certain connection, but Howerd’s performance feels overbearing both as an actor and in his characterization—and I've never been particularly fond of him anyway—so he diminished any sense of nuance or refined comedy. "St. Trinians" seems to be moving closer to the “Carry On” films, abandoning the earlier installments’ spirited energy. It isn’t a bad film, and some of the jokes remain quite lively, but these stories have reached their limit, as far as I can tell.

Source on TMDB