Doing practical science in the primary classroom requires a teacher to show true grit. Thirty children in six groups of five are competing for space, for toy vehicles, for blocks to make slopes with and for a selection of "road" surfaces offering different degrees of frictional resistance. Oddly, these include carpet, wood, sandpaper, plastic, aluminium and rubber but not Tarmac.
To replicate real-life motoring conditions, our science leader has cunningly made sure that the number of vehicles massively exceeds the number of roads. The result is congestion, chaos and carnage. Ten minutes into the lesson, gridlock turns to road rage. Ryan's petrol tanker has deliberately wiped out two hatchbacks, a Porsche 911 and Lady Penelope's pink Rolls-Royce. Katie is in tears, Bradley has to be restrained and Jennifer is putting in a claim for whiplash.
It's like the Wild West in here, so it's time for a teacher to do what a teacher has to do. Like a diminutive Rooster Cogburn, but without the eyepatch, I keep both barrels of my annoyance trained unerringly on the baddies, daring anyone to make the first move. "Keep that finger on your lips where I can see it," I bark, as Nathan attempts to scratch his nose.
While I am composing a stern warning in my head, I happen to glance out at the frozen wastes of the playground. For more than a week, nobody has been allowed to venture out on to the ice and snow. This is because we live in a litigious age and any head allowing pupils to put themselves at risk of a weather-related injury is likely to be hung from the nearest playground-cam by our parent vigilante association.
What happens next is not only impulsive but bordering on the reckless. I do not have the written permission of parents to take the children outside. Neither have I thoroughly considered, by way of a risk assessment, the possibility that someone might fall down and bang their head, get freezing snow shoved down their neck or fall victim to an illegal snowball attack.
But then, why should I? This is a legitimate practical science lesson - an opportunity for children to study the effects of reduced friction in the context of having fun and taking risks.
Our ice slide reminds me of the good old days before packs of predatory lawyers stalked school gates looking for easy pickings. Soon we are reliving the days when frozen playtimes meant lines of children taking turns to skid world-record distances at breakneck speeds. A bygone age when accidents were frequent but rarely serious because the truth is that children are far more resilient than adults assume.
When we get back into class they are red-faced, beaming and filled with the knowledge that nothing reduces friction quite like ice polished smooth by inappropriate footwear. And the good thing is that nobody sustained multiple fractures or fell victim to hypothermia, so by and large I think we got away with it.
"Do you know anything about that slide in the playground?" the caretaker asks the next morning. He reminds me of John Wayne, because he is walking gingerly in a way that suggests his coccyx is bruised from spending too many hours in the saddle, which is odd because he doesn't have a horse.
"Is there a slide in the playground?" I say, trying to look innocent.
He aims his shovel straight at me. "Not any more there ain't," he says. "It's been well and truly gritted."
Steve Eddison is a key stage 2 teacher at Arbourthourne Community Primary School in Sheffield.