If you can t police, monitor or enforce a rule, don t have it. If you re smart, you d say, Hey, Scar, welcome to our family. Enforce the important stuff, not the little stuff. All the little rules poison relationships. Teens have an allergic reaction to trying to control them.
Friends pay attention to their friends, while parents often don t take the time.
One of the things teens hate is being lectured to. Parents must earn the right to ask questions. This is how parents who have influence earn influence. Parents often make kids sorry they ever opened their mouths. One of the marks of a really good parent is when you ask questions that get bad news.