Holly Newton's murder at age 15 by her ex-boyfriend in Hexham sparked her mother's campaign to change UK laws that don't recognize domestic abuse victims under 16.
Schools are not separate from society, rather school is a smaller society in itself. Less crime and violence will not happen without focus on better education.
Since the 19th century the justice system for juveniles has been constantly evolving. There's no clear-cut answer, but research and expert testimony suggests early intervention is a crucial element.