The 1-2-3 rule, also known as "1-2-3 Magic," is a parenting technique developed by Dr. Thomas W. Phelan to manage children's behavior effectively and calmly. It is designed to encourage compliance and reduce disruptive behaviors in children aged 2 to 12 through a straightforward, consistent, and non-emotional approach to discipline. The technique emphasizes clear communication, structured consequences, and maintaining parental composure.