Continuity mistake: When Flash is writing Theft next to no.6 on the board, Blackmail has appeared next to no.5 - Flash couldn't have written it on the board previously because when we see the board (before Theft is written on it), there is a blank space next to no.5.
Continuity mistake: When the girls are crawling back along the cable, there is a shot from just in front of Steven Fry which shows them behind him, when every other shot shows that the cable is over the audience.
Continuity mistake: When the bank manager hands Miss Fritton the foreclosure notice, she is wearing a dark floral blouse, a black patterned vest and small pearl earrings. Then, when Beverly gives Miss Fritton the "red" and "blue" pills, Miss Fritton is wearing a completely different outfit and large mabe pearl earrings. She reverts back to the original oufit/earrings when she speaks with Carnaby. (00:35:40 - 00:37:30)
Continuity mistake: When Flash and the girls are going through the 7 Laws of Crime, kidnapping is written on the board next to the no.4. When it comes back to the scene a little later, Kidnapping is no longer on the board.
Continuity mistake: When Flash is teaching "The 7 Laws of Crime," he writes "extortian" which is spelled incorrectly with an "a". Yet, when he says, "If you don't start using your noggins...," the word "extortion" is spelled properly with an "o", but then it reverts back to the incorrect spelling in following shots. (00:40:30 - 00:43:35)
Continuity mistake: On the school trip to the National Gallery, Kelly finds the paintings location on the far wall facing her, with marble trimmed doorways behind her within an open area, directly opposite the painting. The girls plan is based on this location. However, when Kelly, Taylor and Andrea reach the painting during the heist, entirely different walls with paintings are opposite the painting. (00:45:55 - 01:24:20)
Continuity mistake: When Flash gives a lesson on crime, he asks for ideas, and the girls raise their hands. In the shot from behind the girls, the first girl he points to for an answer sits at the very left (his right) of the class, and we also see Taylors back as her hand is raised, who sits towards the center of the class. However, in the next close-up its Taylor who answers with extortion. (00:40:20)
Continuity mistake: When Annabelle is in the shower, the overhead videocam turns and we see its feed on the laptop. In this shot, as it pans the shower from left to right, the shelf is visible on the right wall, with nothing hanging from its hooks. However, a few shots later a girl removes the towel and robe that are hanging from those hooks. (00:09:45)
Continuity mistake: At the start, when Annabelle and her father drive past the schools front gate, the trees are in full bloom, covered in white flowers. Yet in the next shot from behind the car, the trees are bare. Then when Flash drives up to the front gate, the flowers are back, but in following shots the flowers are gone again. (00:01:35)
Continuity mistake: At the very start of the hockey game, in the shot just after Matron blows the whistle, the scoreboard is visible behind the girls and it reads "St. Trinian 1 and Visitors 3". It's actually four shots later that Cheltenham are the first to score, which then makes it St. Trinian 0 and Visitors 1. (00:27:00)
Continuity mistake: On Miss Dickinson's first day, when Matron hands the new teacher the glass of her latest concoction, the slice of lime garnishes the rim, but in Miss Dickinson's close-up the lime is floating in the drink, then it's back on the rim just before it's back in the drink once again. (00:18:40)