Half a century of cynicism has ripped the heart out of St Trinian’s. Back in 1954, Alistair Sim could dress in drag and naughty schoolgirls could run riot on the big screen and it was still good, clean fun.

But innocence is entirely absent from this extremely dubious addition to the big-screen adventures of Ronald Searle’s cartoon creations.

There’s nothing wrong with being risqué or irreverent, but here is a film aimed at younger audiences which glorifies – and this is by no means a comprehensive list - underage drinking, drug-taking, bomb-making, bullying, cheating, promiscuity, stupidity, verbal abuse, anarchy, vandalism, the use of guns in schools, and the sexual objectification of minors.

Heavily involved in this harmlessness is executive producer Rupert Everett, filling Sim’s size tens as both school head Miss Fritton (previously Millicent, now Camilla, with a hairstyle to underline the comic point) and her sneaky brother Carnaby.

Carnaby’s snooty daughter Annabelle (Talulah Riley) is mortified by her transfer from Cheltenham Ladies’ College to St Trinian’s, especially after an eye-opening orientation from head girl Kelly (Gemma Arterton).

But whether they’re geeks or goths, fearless first years or posh-totty prefects, the whole school must unite to fight the tyranny of education minister Geoffrey Thwaite (Firth) and somehow come up with half a million quid before the bank turns the school into condos.

With help from man-on-the-outside Flash Harry (Brand), the girls hatch a scheme to snatch Vermeer’s Girl With A Pearl Earring from The National Gallery. And they can only do it by reaching the final of Stephen Fry’s TV show ‘School Challenge’.

“You’re going to steal Scarlett Johansson?!” squeals gorgeous dimwit Chelsea (Tamsin Egerton). Not an encouraging response from one of your quiz team members.

It’s a rare moment of subtlety in a script that doesn’t even bother to double its entendres. Yet where junior viewers lapped up every naughty word, accompanying adults were unmoved.

The film partly makes up for its ‘F’ in attitude with high marks for energy and the enthusiasm of its cast. Brand, in particular, deserves special mention for not making Harry a total creep. It will come as a relief to George Cole, who made the role his own way back when.

But, heavens above, is nothing sacred to the Class of 2007?

The spirit of St Trinian’s is perfectly captured in the closing song by Girls Aloud: “We are the best / So screw the rest / We do as we damn well please.” Charming.

Elliott Noble