Don't worry, I once got called not only mean, but ugly too!!! By a child i'd never even taught! This same child spread rumours that I was really strict and was going to be teaching *gasp* year 6 next year!! After speaking to said child, and terrifying them even more no doubt, I decided that actually kids just love to wind eachother up and will copy what each other say! I don't think it's unreasonable to expect older children to sit nicely and quietly when you are talking and also to have expectations of how much work should be done. In my experience this is a lot harder when you are a supply teacher as there will always be children who think "woo hoo supply teacher, easy day!!"