That all parents must attend parenting classes. We have drivings licenses to drive a car. Yet there’s no such skill requirements for parents on how to raise children. Cost of dealing with miss raised children is very high.
If you start mandatory parenting classes, you have to start mandating the ‘correct’ way to raise children. There are HUGE cultural, religious, financial, and educational barriers to implementing a one-size-fits-all parenting regime. Good luck with that!
I don't get the jump from parenting classes to "the correct approach".