Have just read OP. I live in a part of London where relatively high numbers of of teenagers have been stabbed and there have been several murders in the last couple of years.
TBH my 14 year old son chooses not to hang around outside ever. I am very glad about this as I think this is a streetwise judgement of his.
He has not been kept off the streets by us - he used to play out with his friends from the age of 5 or so - not too far away, just down our road which is quiet. Then, around the age of 10 or so, he stopped wanting to play out it as he found it boring.
Later, when he went to secondary school and saw incidences of teenage gang behaviour, he found the idea of hanging around outside too risky.
He avoids local gangs and as he is not in one, feels vulnerable. He has already had his mobile phone taken off him in a local park (on a sunny day at 6 pm) with a threat of mugging. Now, he will only go out to play football or cricket in the parks if he has arranged to meet a few good friends - he would never just turn up by himself and join in a match.
Wierdly, my 8 year old in a way is safer IMO. He plays out in our street - just a few houses away, with a group of neighbouring children around the ages of 7 - 12. He loves this and there have been no problems with crime or gangs. I think there's a good chance he too will stop wanting to play out when he reached secondary school age.p
TBH, I think teenagers are more at risk here. This is how my oldest son sees it, anyway.