Well even from Promary school we all got told that almost certain death was gaurateed if we rocked back on our chairs, every teacher knew one child who cracked their head open etc,
Also later on in Year 9 when starting woodwork there was always one guy our teacher explained that got their 80's style hair caught in the woodwork drill, this guy must of had a tiny head because no way a human could get their head in that gap!
However these fibs and trucks worked and no one died in all my school time! As predicted