My mom works as an assistant teacher at a primary school, and describes one of the children as being unbearably behaved, violent and rude and always throwing tantrums, yet when he’s with his grandma he’s a little angel. Why? Because his grandad spanks him when he’s naughty.
To which, not at all unexpectedly, my father responds: “Speaks volumes, doesn’t it?”
Referencing a child who’s better behaved in the presence of a violent authority is like pointing out that your employees will work harder if you push a gun in their face

Hell, yes. It says two things to me. First, that you can frighten people (particularly children) into doing what you want them to*. And second, that this boy’s grandfather has condemned his grandchild to never accept the system that he will have to endure for twelve odd years, by setting a standard of discipline that nobody else can reach. Quite apart from the fact that punishing a child is a stupid way to teach them right from wrong, the fact that this boy’s parents won’t, and teachers can’t, physically punish him put him in a position whereby any punishment pales in comparison to the beating his grandad gives him. What is a telling off, or a detention, or being sent to the naughty room, when you’ve had somebody belting red your backside?
Regardless of whether it’s acceptable or not, punishing children is stupid and immensely shortsighted, and in this case the negative impact (if you’ll excuse the pun) has been even greater than normal. “Speaks volumes, doesn’t it?” Man. Referencing a child who’s better behaved in the presence of a violent authority is like pointing out that your employees will work harder if you push a gun in their face.
*This piece of information should be essentially useless, since nobody should think that frightening somebody into submission is an effective way of achieving anything.