Everyone. No questions asked. Even rude people. They learn to respect people now, they will have a better understanding of how to treat people when they get older. Respect is one of the biggest values of life. It also develops their personality. They will be more respected by others if they show respect to others.
You never know when, where, and why some people may be disrespectful, but it is not a reason to be disrespectful back. Respect is earned, and it shows if someone is a respectable person or not. It is a quality of life, whether it is being a friend, family member, co-worker or boss. That is a quality that will carry a person through life.