Nine-thousandth cousins four million times removed. 
As I recall it was because it was thought that fossils should only be studied and removed by scientists. Apparently no one bothered to note that the formation they’re found in there extends for over a mile in one direction and an unknown distance in another, or to think ahead and realize that fossils would just fall into the county ditch.
As for safety, the only incident I can remember in over thirty years of sixth-grade classes going there was a teacher tapping a bit too enthusiastically with a rock hammer and knocking off a chunk of material big enough to hit her in the shins.