First, get the children off all the sugar and chemicals in food.
Second, use the rod (Bible): a fiberglass balloon stick; a ping pong paddle, a 3/8 inch wooden dowel rod, a wooden spoon, a long wooden old-style hotel shoe horn, etc.
Avoid hitting the head, the spine/backbone, skeletal joints. The fatty tissue of the buttocks and back of the thigh are useful for inflicting the rod——not for simple errors, or forgetfulness, etc.——but for obvious rebellion against parental authority, or lying, refusal to stop touching objects they are instructed no to touch.
At about nine months of age, or earlier, a child can be placed in a chair and trained to be still. Five minutes per day for a week. Seven minutes per day the next week. Ten minutes per day for ten days.
Soon, children will learn to sit still for one hour, then two, then three. They can be trained at home initially to be admired and even doted on by people in restaurants and waiting rooms for their good behavior.
That’s how you train a dog.
My parents took the ball off the paddle ball and used the paddle on me.
I remember once...ONCE...acting up in public.