Taking personal responsibility for one's own safety is not something that is stressed in our society. This is especially true for children. Children are innocent, pure, and it is thought that they should be able to live a life devoid of responsibility for their own safety. They are supposed to be protected.
Unfortunately, that is not always the case. Assaults, both violent and sexual, can happen at any time. There have been instances of children being sexually assaulted while out to dinner with their family, in the public restroom. I believe an important thing to remember is that anyone, at any time, can be assaulted.
I don't say this to instill fear. Indeed, if Steven Pinker is to be believed, human to human violence is on the decline. I personally expose myself to environments which might be considered dangerous, but when I do so, I take steps to safeguard myself.
Firstly, I believe awareness is key. Knowing where the people are in your environment, what kind of environments are dangerous, and when it is time to leave are all important parts of personal safety.
Second, once awareness as been established, a mental framework for setting boundaries and remaining assertive in the face of aggression must be established.
A small example: While taking part in a political protest march, a loud, aggressive homeless man began walking near the line of people. As soon as he came close to me I stepped away, keeping him out of striking range. A woman behind me, chose to ignore him. She got punched in the head. Don't do that.
After awareness and boundary setting skills have been acquired it can then be helpful to learn certain martial arts techniques to defend against an attacker. Without the previous two skills, even an experienced martial artist is at an extreme disadvantage in a dangerous street situation.
For children, the same principles apply. Though they may not be able to effectively protect themselves using martial arts, they can learn awareness and boundary setting techniques which could save them if they were to be assaulted. I think this is something that should be taught in schools. The "Just say no to strangers," policy is a little to simplistic, especially since a large portion of sexual assaults are perpetrated by people who are not strangers.
It's not fun, it isn't pleasant, but I believe these are things we need to speak to our children about. These are skills that our children need to learn.