I teach my children that sometimes it is good to tell lies. In my experience, it is safer for a child to tell a lie that indicates adult help is at hand than to get into a physical fight.
Having said that, I also make sure my kids have a level of confidence in martial arts so they have the skills to fight if necessary.
I wrote a hub called 'Why children should be taught to tell lies' and the vast majority of people who left comments agreed with me - but I did come under fire from one person for suggesting that children should sometimes lie.
It has worked well for my kids in the past. :)