The ball strikes me full in the face and rebounds over the bar. "Are you all right, Mr Eddison?" asks Ryan. I have accidentally walked in front of his free kick. He leads me gently out of the penalty area and deposits me on the touchline. He thinks it's not safe for me to wander unsupervised around a football pitch during playtime and he's probably right.
My age is beginning to show. Last weekend, my daughter got married and it still feels like the morning after. Emotional fatigue and physical exhaustion are sprawled across the sagging three-piece suite of my being while the slumped figure of financial ruin lurches backwards and forwards in a rocking chair with his head in his hands.
Like Christmas and pre-election promises, with weddings all sense of economic restraint goes out the window. As a Yorkshireman I find this difficult to cope with. My only consolation is the thought that in a couple of years' time I may have someone to call me grandad. By that I mean someone I'm actually related to.
I've been called grandad many times in recent years. It's an easy mistake to make in the excitement of the learning process. Elderly males all look the same to primary students and I have the right credentials. These include partial deafness, memory loss where names are concerned and a tendency to leave reading glasses close to vortexes in the spacetime continuum.
There was a time when students used to call me dad by mistake but that was years ago. I don't remember when grandad took over but I do recall the first time it happened. The shock caused me to shave my moustache off and buy hydrating moisturiser for men. These days I'm more relaxed about it. In fact, I'm hoping our daughter's marriage may be a sign that she and her husband are considering starting a family.
I mention this theory to my wife but she is not convinced. "They have careers and a mortgage to consider. It could be a long time before they have children," she says.
"But my best grandfathering years are passing me by," I protest. "Will I still be able to teach my grandchildren to ride a bike 10 years from now? Will I be able to kick a ball about and demonstrate the Cruyff turn while using a walking frame? How will I show them the reverse sweep when the umpire of time has given me the finger and sent me to the pavilion?"
My wife tells me that I just need to be patient, but my own grandad was in his seventies and crippled with arthritis by the time I was born. I have only a hazy recollection of him smoking his pipe in an armchair next to the wireless. When I close my eyes and concentrate on his voice all I can hear is the ghost of Billy Cotton on the Light Programme.
Somebody screams a warning and I look up just in time. I control the ball on my chest; wait for it to drop and volley it into the back of the goal.
"Nice one, grandad," says Ryan.
Steve Eddison teaches at Arbourthorne Community Primary School in Sheffield