You're partially right about what is causing the wave of youth stabbings. You think it's because parents don't batter their kids anymore. It's not. It's for 2 reasons. It's because parents batter their kids for the most trivial of reasons to the point that it becomes abusive as that's the only way they know how to 'control' children and those kids grow up seeing violence as being acceptable. It's also, and you're right about this, a lack of discipline. Parents are too absorbed in their own lives, smartphones, social media, reality TV, drunk, drugged up and focused on their latest boyfriend/girlfriend to give their kids any real positive love and attention, to have conversations with them about morals and what's right and what's wrong.
I spent 7 years working in a school in Leeds where I would see kids getting battered and being called an 'effing muppet' at the school gates every afternoon for having dirty clothes, cos it meant that mum had to wash them. Or kids whose parents were never involved, allowing them to do what they want, when they want including kids swearing at parents without any consequence because 'it's too much hard work to discipline them and it's the school's job to do that'.
As I said before, it's lazy parenting. These kids had absolutely no chance in life except to get away from those families as soon as possible, which some of them have been able to do and are living happy, successful lives. Many others though are in prison.