The smart kids knew to stay out of the way. The fast kids didn't, but could spot it or hear a warning in time, and they also got away. Conclusion? Only stupid, slow kids got hurt. Isn't that evolution? We shouldn't have banned the things, they should have been mandatory. We should have had extra cops on duty to spot-check and make sure kids were playing with them.
This will all be in my new upcoming book "Why We Need to Increase, Not Decrease, Speed Limits in School Zones".