I have found that if I take out my cell phone and pretend to take a pciture of them - it tends to discourage them (My phone has no camera) - it does take my time and slows me down - but worth it to me - if I had a real camera phone I would take a real picture in case something did happen to me. I know I would almost never be able to pick anyone out of a lineup -kids usually wandered off muttering when I explain to them what I am doing and why (taking your picture to show police)

ps - I am a lawyer who does criminal defense - the girls are becoming more and more like boys in some types of crimes that they were not usually involved with in the past.