The teacher said in front of the child that his grades were behind him. What should I tell my children as a parent?
I think since this kind of thing is a fact, there is no need to avoid it deliberately. Just tell children that people are gregarious animals, so if you want to survive in this world and not be bullied by others, then you can at least be above the average position, and so can learning. You can't hold others back. No one likes to be dragged down by others. I hope you won't bother next time.