I walked home through Bethnal Green and Hackney at close to midnight yesterday and survived to tell the tale. Would rather do that than the same walk in parts of Chiswick and Kew to be honest - it's very quiet there, and lots of trees so very dark and no one around so much scarier at night than a busy street!
Not using the bus at the moment but have spent a good chunk of my youth on night buses in London - a few drunks and weirdos, some clearly very unwell people and yes, once a fight between some teens who claimed to have a knife although no evidence of it. Honestly the rest of us on the bus were basically invisible to them. They aren't interested in you.
I have had my car broken into two years in a row while visiting friends in a tiny village in Yorkshire and was burgled when I lived in Bath for six months and my phone snatched out of my hand in Exeter. And as yet, never been burgled in London (touch wood)
Did have a letter through my door once from the police asking if we'd heard gunshots the previous night (we had not) and we've had some issues with people smoking heroin in a old phone box but they've done no harm to anyone beyond themselves.
If I look at the crime stats for my local area and zoom in to my estate, it looks dreadful. Loads of anti social behaviour crime etc, but most of that is one very mentally unwell person who was clearly desperate for help and used to essentially call the police on themselves and go and sit in the middle of the road. Quite a bit of domestic violence in that household as well so explains some of the assault crime listings. But little bearing on the lives of the rest of us
I am not entirely glib - I wouldn't walk home alone drunk, I stick to main roads and I keep my phone tucked away because I have witnessed some highly skilled high speed snatchings of them. I grew up in a fancier part of West London and teens are at higher risk of being mugged by fellow teens - this has always been true. But most are never actually mugged.
And eventually your teens will be going off to Shoreditch, Deptford, Soho, Dalston, Peckham etc because it is where the cool stuff is - so they will venture outside what ever suburb you choose anyway.