The other day I took a whole lot of kids to the playground. They played for a while and then they noticed a young guy cleaning up the place. He was collecting rubbish and tidying up. They kept playing and watching him and giggling and I kept knitting. All of a sudden they erupted into laughter. I looked up to see one of the girls tipping a bag of our lunch rubbish all over the ground. There were food scraps and tinsel and bits of wrapping paper and confetti and glitter that we'd been careful to collect. It was a real mess.

I was horrified. I apologised to the man and asked him if he could get the girls to help him clean it up. He said no and that he'd seen worse and that it was his job and that he'd do it.

I turned to the girl who had done it and had no idea how to deal with her. She is not my kid. I gave her a bag and told her to get the big bits. I told her she had behaved badly and wrongly and disrespectfully. I told her that one day it might be her cleaning for her job and how would she feel if someone did that to her. I probably went on about it too long and then when I got them in the car to take them home I went on about it some more. To be honest I had no idea what to say or do though and I'm pretty sure that I made no impact on her.

So how do you discipline other people's kids? Is it my responsibility to teach them right from wrong? What would you do in that situation?