A child who lies has made an error in judgement. Observe your child calmly in order to determine the reason. ( Parents usually know when their child is lying. Parents are never as easy to deceive as the child believes.) Once you discover the lie the parent can deal with it as a teaching moment. Montessori explains, "What matters is not so much correction in itself as that each individual should become aware of his own errors, each should have a means of checking, so that he can tell if he is right or not."1 So we can help the child recognize his own mistakes; we all make mistakes, even parents. Montessori believed that children should know the ten commandments. It is a simple matter to remind him of them. Boundaries need to be established and continually reinforced through reminders and explanations.
1 Montessori, Maria Absorbent Mind. New York: Henry Holt and Company