Similar story. I was in elementary school and fell off the monkeybars and landed flat on my back and knocked myself out, surrounded by kids. I woke up later and everyone was gone, so I got up and went back to class. I got detention for being late. When my parents asked why I "skipped class" I said that I didn't know and was grounded for not telling the truth.
I did other dumb things, mostly around bodies of water (cliff diving, rip currents). I'm surprised that I'm not dead. As an adult, I'm afraid of everything.