As a parent, I would have demanded the principal prove to me or to anyone that what the toy soldier was actually holding was a toy gun. He could have been holding a pool cue, a golf club, or a surveyor's tool.
It can't be done. She would have had to withdrawn her "weapon" ban (since when is the depiction of a weapon a weapon, anyways?).
In order to combat this absolute lunacy, one needs to get into a certain state of mind. Gawd forbid, but you have to think like them sometimes. If these moonbats actually think these tiny toys are weapons, then you can point out to them that they are too small to actually fire or hurt someone, and maybe they are something else. Maybe they are pole vaults. You have to talk to them like they are children, perhaps reassuring them.