I fold my arms and wait for the hullabaloo to subside. It has been a loopy sort of playtime and some of the giddiness has followed the children back into my classroom. It's not difficult to spot the cause.
"That's a strange-looking rash you've got there, William," I say, once a degree of calm has been established. "I think you had better let me take a closer look at it." He comes to the front of the room, wearing what appears to be a rare skin condition. He is also wearing the sort of grin that requires his teacher to take a deep breath and count to 10. I shut down sporadic bursts of giggling one by one with my steely gaze until William is the only child left smiling. Not for much longer, sunshine.
With the aid of a magnifying glass, I carry out a detailed examination of his rash. My conclusion is that the situation is much more serious than I first thought. William is not sure whether to grin or to look worried.
My investigation reveals that his face and arms are covered with identical green spots vaguely reminiscent of trading stamps. If this were the 1970s I could swap him for a lava lamp and an Instamatic camera. Each spot is about a centimetre in diameter and bears the outline of something resembling a four-leaf clover. Amusingly, he has one on the very tip of his nose. Curiously, he has one in the centre of each lens of his glasses.
I replace the magnifying glass and ask him questions about the general state of his health. "Do you have a headache, William? Is your throat sore? Are you suffering from stomach pains? What about pins and needles?" When he answers no to each one, I frown deeply.
After shushing the students who are desperate to help me diagnose the true nature of his condition, I go on to make a solemn announcement. "I'm sorry, children, but I'm afraid it looks like William has contracted green measles. Unfortunately it is the worst kind of measles. It's highly contagious and often fatal."
Isabel asks me what contagious means and I explain that it means you can catch it very, very easily. Several children who have shuffled their chairs closer so as not to miss anything begin to shuffle them back.
"I know what fatal means," says Ryan. "It means you're going to die." To exemplify this he makes a desperate choking noise. There is yet more shuffling of chairs.
"Don't worry, William," I say. "It's not fatal if you diagnose it early and get the right treatment. And as I distinctly remember that you had no sign of green measles before playtime, I think there is a good chance you can be saved. Now, before I ask the office to ring the emergency services and an ambulance comes to rush you to hospital, can you think of any other reason why you might be covered in bright green spots?"
William examines his feet for several seconds before taking something out of his pocket. He hands it to me without looking up.
"What's this?" I ask.
"It's my grandma's lucky bingo dabber," he says.
"Ah, William, you are a card," I reply.
Steve Eddison teaches at Arbourthorne Community Primary School in Sheffield