Yes, I see what you mean twigs.
I would say though, that integrity also can be a moving feast. What is fair to one person may not be to another.
Nevertheless, I would say that treating them as you wish them to treat others is probably the most successful ways to encourage integrity.
However, growing up also means learning that things aren't always fair and consistent and being taught how to cope with this is also important. You know, the whole thing about humans are never without flaws and that we will always love you irrespective of what flaws you develop We might not like those flaws, but we will always love you.
Also that they should try and understand why others views of integrity is different from theirs rather than hold an arrogant view that their definition is always better!
Although not particularly religious myself, I do find that the 10 commandments are a good starting point for a community to operate with integrity. If you take out the obviously religious ones, that is.