Keep them away from schools IMO. Every adult at a school can tell kids what to do and they are supposed to do it. Of course only the "good" kids do what they are told. Could you ever take the time to actually know all the adults your child interacts with at school?
Teach them the differences between morality, ethics, & legal complications (age dependant).
Spend time with them and make sure they know you care about them. I have seen to many kids, and adults, that let bad/evil things happen to them because they don't believe they have any worth.
Try to create a workable "chain of command" that the kid can go to if they think this or that person is doing something that scares them or is wrong. I have to many friends who were victums of child abuse (of every type) were one whole side of the family was involved activly...and the members of the other side of the family that knew about it did nothing
Make a list of things that are bad no matter who does it. And listen to them.
I used to drive school bus, and I still don't understand how parents can let there little kids go into the real world without someone they know and trust watching their kid.
I guess from the things I have seen I won't let my kids (when I have them) be alone around people I don't know and trust 100% till they are at least 8 or 9.