Schools have all sorts of drills!  Do you not remember fire drills, tornado drills, and in the 1950s, the bomb drills of getting under desks and covering your heads?  I don't think any of us were traumatized by those.  Firefighters also taught us the "stop, drop, and roll"  technique in case we were ever on fire.  Those drills, just like reciting multiplication tables, the alphabet, memory verses in Sunday School are all part of learning.  We cannot keep all bad things away from our children as much as we would like to.  If you watched the television series on THE BIBLE, you saw that children in those days saw much worse things.