I'm not an instructor, but this question brings to mind a few memories from my elementary school days that I thought I'd share.
Predators were a problem I never encountered, but I had to deal with bullies aplenty. From the ages of 6 to 9 I was taking hapkido. (Looking back now, I see that the hapkido instruction I had didn't have much grappling training, but that's a separate issue.) I was a small kid, and I was usually thought of as a nerd, so I guess that made me seem like a good target to some bullies that didn't know better. I actually started a couple of the scrapes I got into, but we won't go into that here.
When kids who were bigger and older than me wanted to threaten me physically, they tended to get in close. I remember them trying to pick me up, put me in headlocks, ect. My typical response was attack them in sensitive areas. Nose gouging can work wonders.
There were also a few fights I got into with some of my peers (who were also usually stronger, if not bigger). These tended to be more like boxing matches, with our classmates gathered around watching, but without rules. My secret weapon here was my nose- tap it too hard and it bled. When the other kid saw a little bit of blood, they always seemed to think they won for some reason, and they would drop their guard, giving me a chance to rush them.
As far as bullies go, I think the most important thing you can teach young kids is aggresiveness and tenacity. Of course, the flip side of this is that you have to teach them how to avoid physical conflict, or you risk creating a bully.
For adult predators, I think some of the same things would work, such as being aggressive and attacking sensitive areas. Obviously, making noise and attracting attention would be good things to teach too.