It seems to be a bad idea to me to deliberately inflate the self esteem of children. If they are smart they notice the gaslighting, if they are not they develop impostor syndrome. Both undermines their ability to properly judge and regulate their relationship to the world.
“You tried harder than the smart kid, but you still failed” is a better feedback than “you were playing fortnite all afternoons last week while you pretended to yourself that you would be thinking about calculus”?