Apparently you've never raised children nor spent much time round them at that age. I recall a childhood friend of mine around that age who climbed a tree, then fell. She didn't try to break her fall and as a result, landed on her shoulder resulting in a broken collar bone. The height was only about 10 or 15 feet. We asked her why she didn't put her hands out to break her fall. Her answer was "I don't know, it happened so fast." Why was she climbing the tree? "I don't know, I just wanted to get a better view from up high". Had she landed in a slightly different position, she well could have ended up with an injury similar to MS.
Kids of that age do reckless things, whether they're smart or good or whatever.