Congrats to the “winners” but I recommend that all reading this post also read:
Punished by Rewards: Twenty-fifth Anniversary Edition: The Trouble with Gold Stars, Incentive Plans, A’s, Praise, and Other Bribes
Both books were written by Alfie Kohn and they are not just his opinion. He has read and summarized a lot of research.
I also recommend reading Skin in the Game, by Nassim Nicholas Taleb. There he mentions this phrase by Wittgenstein:
Anything that smacks of competition destroys knowledge.