We are a family that is in the process of adopting four siblings, bringing our total number of children to seven. They all are great kids and we seem to be adjusting pretty well, with the exception of one. He's 12 years old and has started lying all the time, usually about small things. It doesn't matter if he knows he will get caught, because he will lie anyway. We have tried all kinds of things -- punishing the bad behavior and rewarding the good. He seems to be old enough to understand that it's wrong, but won't stop. It's ruining the family atmosphere.
To reestablish the family atmosphere, my first suggestion is to tone down the attention you give to his lying. Instead, focus on good things happening in the family. Next, consider these questions: Is he lying about important things? What does he lie about? What does he get out of lying? How does it make you feel? That can be a clue.
Is he your own or one of the adoptees? If he is your own child, he may be seeking attention in the only way he knows how and may fear the loss of your caring with the influx of four more siblings. If an adoptee, there may be some grieving, loss, and trauma involved. At the very least he may be grieving the loss of his natural family, no matter how bad that living situation may have been. He may be feeling divided loyalties. He may not know what he is feeling!
Assurance on your part and normalizing the experience may help, but a general support group or a grieving group for children his own age may be even better. Check with the school to see if the counseling department offers such groups.
If the lying continues and is serious, I encourage you to seek out a counselor in private practice. The school counselor will give you referrals of professionals.