HULL Truck Theatre has had a bumpy year at the box office, attracting new audiences but losing regulars in bigger numbers, prompting thoughts that executive director Andrew Smaje should go back to the drawing board.

In the meantime, Hull Truck goes back to the classroom for Tim Firth’s riotous Christmas comedy, The Flint Street Nativity, first seen on television with York actor Mark Addy in a donkey head, and then adapted for the stage at the Liverpool Playhouse in 2006.

The director of that stage premiere, Matthew Lloyd, is in charge of the Hull revival too, and his production is deservedly drawing the kind of numbers that sees the sides of the theatre filling up too, which is such a boost to the atmosphere. A case of go Firth and multiply, you could say.

Lloyd has picked a cast that combines television stock with Hull Truck repertory players for Firth’s re-creation of the highlight of the primary-school Christmas calendar, the Nativity Play, here performed on a James Cotterill set that mimics the improvised, make-do designs of such shows.

“There’s no treachery assassination, double-dealing, deceit, coercion or blackmail that you encounter later in life that you will not have been prepared for in the classroom,” says teachers’ son Firth, who brings to school the clash between teamwork and individual desires that flavoured his comedy in Neville’s Island, Preston Front and Calendar Girls.

Firth’s salient powers of observation are as sharp as ever in his account of a class of seven-year-olds mounting the Nativity play at Flint Street Infant School. Ostensibly they are under the control of the often mentioned, never seen Miss Horrocks, but the children pretty much do their own thing, much like Mary’s donkey, a holiday relic that swears in Spanish.

Brookside old boy Neil Caple’s Narrator is determined to keep the play going, flattening everything before him, voice and all, but he must contend with petty squabbles, rampant egos and the disappearance of Peter Crouch, the school stick insect.

Malton musical theatre actress Lauren Hood, the triumph of Hull Truck’s summer in The Rise And Fall Of Little Voice, shows another side to her repertoire, switching from the timid Little Voice to the ruthless little madam playing Gabriel, so determined to gazump Mary’s role. Less hard-nosed than Alicia Roberts’s interpretation for York Stage Musicals last month, she expresses the girl’s inner vulnerability.

Elaine Glover, from Hollyoaks, thrives on the spat for Mary’s role between her, class swat Jenny B, and Hood’s usurping classroom trouble-maker. The climax of their struggle is the prime comedy moment.

Rep regular Frazer Hammill switches to good effect between two roles in headgear: a NASA-fixated dreamer designated the role of the Star of Bethlehem and the loveable lad who grows so attached to his Ass’s head.

Another rep fixture from this year, James Holmes, has the show’s best comic timing as the boy assigned to play Herod and Joseph but obsessed with re-enacting the Ally McCoist era on A Question of Sport, while Al Nedjari gives pathos to the lisping new boy who struggles to say “Frankincense” and “Jesus”.

Lucy Beaumont, Rina Mahoney and Laura Elsworthy all add to the fractious fun and the biggest impact is made by former Emmerdale star Dale Meeks, the loner whose Innkeeper makes Norman Bates look like a pussycat.

Firth backs up the mayhem and joy of watching adults play children with two masterstrokes: the children each sing a Carol with new lyrics that tell the truth about their parents, from a child’s frank, hurt or frustrated perspective, and the actors emerge for the finale as those parents, whose behaviour so explains why the children are how they are.

Darkness descends on the play, Firth fuelling the nature-versus-nurture debate, the real-life story trampling over the Nativity play.

The Flint Street Nativity, Hull Truck Theatre, Hull, until January 14 2012. Box office: 01482 323638 or hulltruck.co.uk