I am often asked the question, "What is a good punishment for children who are rude to adulst?" Rather than take this tack, I would rather answer the question, "How can I teach my child to speak respectfully to adults?" I don't like punishment as a way of eliminating problem behaviors because punishment doesn't teach anything but to act a certain way while you are around.
Instead, you need to discuss with the child why he or she is rude to adults. They may only be rude when the are cornered or caugt doing something wrong. In any case, you need to teach the child exactly what to day and then reward the new behavior.
These are called replacement behaviors for the problem behavior. You
must teach and reward them. Practice role plays during your discussion.
Have the child practice what he is to say, in a given situtation and reward it.
The thing is, we teach other things to kids, but we rarely take time
out to teach behavior. It is the fatal flaw to most punishment plans.
With punishment, we take away something for the misbehavior, but we
don't teach anything to take its place.
We also reinforce kids who get an "A" on their spelling test, but we
ignore it when a child improves their behavior. So tell him that he if
he can use what you have taught instead of being rude, he will get a
small treat. Later, you can replace this treat with praise only.
If you think you need a punishment, make sure it fits the crime, so to
speak. If he is rude to someone, he should have to apologize or perhaps
be excluded from the situation.