Angela Singer reviews Groan Ups, which can be seen at Cambridge Arts Theatre until Saturday, October 23.

Sometimes when you go to the theatre you wish you had brought roses to throw onto the stage at the final curtain. On Monday night, I wanted to throw bricks. (OK, just sponge ones).

Adult actors play five children, three boys and two girls, aged six.

The play opens on a Monday morning in school. They tell us what they did over the weekend.

There’s lashings of innuendo, references to a dad overheard messing about with a cleaner up in the bedroom: “Ooh rub that bit harder.”

We learn what one child’s father says leeringly about another child’s mother: “But he still would.”

In subsequent scenes we see them as 14-year-olds and finally as adults.

The set starts off as clever, a primary school classroom with giant furniture, all very colourful and charming.

The tables and chairs get smaller as they get older.

But why once they are teenagers and then adults are we still seeing the suspended Hungry Caterpillar across the ceiling and posters about how to tell the time and times tables? They spend their entire school career in Year Three.

Sadly, there is no depth to this. It’s like a student sketch show stretched out over two hours. The writing is hackneyed. There is a lot of shrieking. No one has explored their character.

Two of the cast speak gently at times, but overall it’s unconvincing clowning. A lot of falling over, a compendium of stale old jokes. Difficult to care about the characters.

In other shows out of this most successful stable (Mischief Theatre, responsible for the Play That Goes Wrong series), the humour works on slickness, speed and surprise. Yes it’s doors falling off hinges and people falling through floors, but not just when we are expecting it.

Here the jokes are so laboured that that you seen them creaking over the hill an hour before the punchline.

With proper characterisation, a thought-out plot and a witty script, the idea that (as Maya Angelou said) we don’t grow up, we just get older might have worked. Sadly, here it doesn’t.

It’s a play pulled out of a cracker, churned out on a production line. Let this character fall over here, repeat the same gag there. Keep repeating it. Then serve it up again. We have a running joke about killing the class’s pet hamster.

Groan Ups may not be the worst thing on the British stage at the moment but I am in no rush to see the other contenders.