Although it might be anathema to the politically correct Thought Police, there can be little doubt that children are occasionally capable of uncommon cruelty. You just have to listen to some of the things they say to each other. One playground remark that I remember overhearing on several occasions during my own schooldays was that somebody or other "had a face like the back end of a bus!" The implication was clear : the person being discussed was aesthetically challenged, a veritable Plug among the more physically blessed ranks of Bash Street Kids.
How I used to hate that pernicious little phrase! Not, let us be clear, out of compassion for the hapless victims of the barb. No, my outrage was provoked by the unwarranted and arbitrary slur on my beloved buses!