Fortunately most of the kids in the hall my kids attend are two faced. Only tonight one of mine was telling me that the kids in the hall are nice and pleasant in front of their parents and behave completely opposite when their parents are out the picture. I encourage mine to have friends at school, who always tell it as it is, are streetwise and realists.
Friends are always tricky, kids fall out all the time. As far as teaching them TTATT I use real life issues, not doctrines. Just ask if things make sense to them, ask 'what if' questions, they are more clever than we give them credit.