As it returns for a second series, Big School really seems to have found its comedy feet.

David Walliams’ performance is still every bit as subtle as his cross-dressing “I’m a laydee” Emily was in Little Britain.

That is to say, not at all.

But Big School is well enough written to survive his camp, asexual gurning and the dream cast add extra polish to an already shiny script.

In tonight’s opener, music teacher Mr Martin (Daniel Rigby) is about to launch his pop career. (His single, written by David Arnold and Michael Price, sounds like an entirely credible X Factor winner’s song.)

Mr Barber (Steve Speirs) has had to take a career change, PE teacher Mr Gunn (Philip Glenister) is now also teaching geography, and even the confident Miss Postern (Catherine Tate) finds herself at a crossroads in her career.

In one slightly depressing piece of casting, former EastEnder Cheryl Fergison replaces Julie T Wallace as the wordless lab assistant who has the hots for Walliams’ Mr Church.

Why depressing? Because making someone the butt of the joke just because they don’t look like Angelina Jolie feels uncomfortably like bullying.

But the real reason for Big School’s success is probably Frances de la Tour.

Even when she’s not actually on screen, just knowing that she’s lurking somewhere in the building as vinegary headmistress Ms Baron is reassuring.

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