Ignore them. The typical adult saying, "just ignore them, all will be fine," sometimes this does work but most of the time it doesn't as ignoring the mean person could make them angry and most likely to act more unkind, if you tell the mean person to stop, or be nice to them most of the time you will be ok as long as you don't say a mean comment back. If you say a mean comment back your just going to argue which is stupid because YOU might be the one to get in trouble, walk away if the problem continues.