Most children who end up being heavily involved in gang crime could probably, sadly, be identified at a very young age by primary school teachers.
Dysfunctional family background, violence at home, older brothers/cousins involvement in crime, disengagement in education by the parents as well as the child, deep and grinding poverty, living in temporary accommodation, regularly moving around often between family members, foster care etc.
All leading to a lack of belief in the "system" - the idea if you work hard at school, you can get a job, earn a decent living, have a stable life, being respected by your community and enjoy a few treats. It is a fantasy to them (because the system has largely let them down so far) - becoming a famous rapper seems far more believable to them.
A youth club alone will not fix that.
An older man comes along and offers them money and status and respect.
They have none of that. It is no wonder they are tempted.
It's impossible for the police to infiltrate a gang of teenagers - their ability to beat the issue by standard policing is very limited.
I'd also advocate for legalising the sale of most recreational drugs through state- owned specialist shops (like booze is sold in Norway). Then the money making opportunity for the older men at the top of a chain is more limited