The note from the school suggested the children walk in pairs or groups, go to nearby shops if they can for help, hand over phones, bikes, etc if confronted. The letter also mentioned the school has been shown photographs of specific individuals to look out for. It seems the police response/visibility on this is really high and that helps. One of my sons was mugged in Dulwich Park with his mate a year ago - he did not have a phone on him and felt more vulnerable as he had nothing to hand over and they wanted to search him. He handed over his bike instead - the charming thugs eventually dumped it as it was a tiny lame bike. I'd say have your kids carry a phone (but do not use it overtly - I suggest my boys pop into a shop if they need to make a call/text etc), a crap phone they are happy to hand over - much less intimidating to have something to offer up. My boys are both happily walking to school, cycling, carrying phones etc despite this note - they are just a bit more vigilant.