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
No Contest: The Case Against Competition.
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.