I agree with the OP, there seems to almost be a shrugging of the shoulders as yet another black child loses their life to knife crime. I don't know what the answer is, but suspect that there is not one move that would change what has been an evolution of behaviour. Maybe more Surestart centres, maybe less acceptance of men fathering children and leaving the mothers (and often the state) to raise them, not just blaming the single mothers left to get on with it. More day care so that said Mothers can get a decent career going, or even just a decent job, encouraging young girls to look beyond the latest boyfriend, encouraging them to see having children as something you do as well as have a career, not instead of.
More black and mixed race role models? Not just high profile footballers and rap artists. How many black male teachers are there? Not many I expect.
idealistic.
All I know for sure is that I would be terrified if I was a parent of a black or mixed race child in a major city, terrified every day they set off to get the bus to school. very few have the opportunity or financial means to move away from the frightening influences on their sons.