Not advocating or giving advice:
In another life for a brief time I was a (mil) combatives instructor, with two twin daughters living in a dodgy neighborhood in Washington DC. When they turned 13 I bought a couple of cow legs every coupla of days for about 6 months for practicing severing the femoral (very similar to a human femoral as far as location and depth) and a handful of other target points 10,000x with a 4 inch tactical blade. Once I was confident that they were skilled enough to do the damage without being disarmed, I allowed them to EDC a blade of their choice.
Luckily, those skills were never needed, likely because other kids and folks in the area knew about it and that was maybe enough of a deterrent.
It's a crappy world. Still not sure it was the right thing to do at such an early age. But it lieu of the people in charge (teachers, cops, etc.) not doing anything to protect my child, the duty of physical protection falls on me.