Ah sadistic old school teachers we have known and hated - pun intended! Our lot did not restrict themselves to plimsolls, canes, rulers, yardsticks ...the list went on and on and it would be unpleasant to dwell. What I do recall is the ability of most to suddenly turn around from writing on a blackboard and hurl a bit of chalk at whoever was playing up and to hit the mark every time. If the problem was of a more serious nature it would be one of the heavy wood block and felt blackboard rubbers chucked at the victim ...and they had the potential to do real damage to heads, bodies ...and windows which is what happened if their target was quick enough to duck or dodge the projectile! I could go on...