A minor act of arson

The lesson was going very smoothly.

Students were getting on with their work and I was moving around, offering help.

Then I heard a yelp. Two boys had leapt to their feet and were desperately jumping up and down. They were putting out a fire.

I was surprised by my calmness. Without raising my voice, I asked the two students to leave the classroom. Speaking to them outside it turned out that they had set fire to some string with a lighter. They admitted that the prank had been more explosive than they had expected. They accepted the inevitable trip to the headteacher's office with good grace.

Two teenage boys enjoying a mini-rebellion. I'd obviously rather they'd have chosen someone else's class.