And if they are doing this, maybe you should increase the amount on the life insurance policies you have on them.
Yes...this is a classic case of, "it was all in fun, until someone got hurt."
Although I will have to admit that I participated is some pretty silly things when I was that age. I remember riding a wagon down a steep driveway. And when someone suggested that we needed brakes, the solution was to tie an anchor to the rear axle. When you start going too fast, throw out the anchor. What we failed to anticipate was the anchor line wrapping around a tree growing next to the driveway. We went from fast -- to stopped -- instantly. Everyone tumbled out on to the blacktop (no helmets back then), and the rear axle snapped.