Kids (and I guess people in general, but particularly kids)...
I don't know what it is... I was a teacher, raised mine & others...
They get hurt like everyone else... but now and then, they will have these moments of accidents where you or I would be in the hospital, and they cry for a minute and they're fine. I dont konw why... maybe they don't weigh enough for their weight to hurt them, maybe they're just closer to the ground. I've seen them hop out of bathtub, go completely head over heels and land... and jump up, completely fine. I'd be in ER with broken hip and a year of rehab... I mean head over heels, and they're fine.
When I was 8, I ran thru a plate glass window (screen door was hooked and I ran at it full speed). I fell down steps onto concrete midst raining glass, landed headfirst. Family thought I was completely dead. I got up and kept playing like it was nothing. I thought I was in trouble for breaking the window. I just fell 10 feet to the next floor, rolled when landed... insanely lucky.
kids have crazy luck sometimes.