First, let's set things straight: Teens value friends before anything else, including parents! Peer relationships are everything. Friends are all-important. They replace the family, in some ways, as the place where daily relationships are played out, where meaningful interactions occur--the back-and-forth working through of ideas and events.
Second, parents need to have greater sensitivity to how much work it is for teens to join groups. Let's take a close-up look. As a newcomer, a teen must establish his or herself to get accepted. This is not easy. Entrance can be negotiated through friends, relatives (e.g., brothers, sisters, and even cousins), and someone you are dating, if they are accepted. After the dating period is over, however, the teen has to maintain the membership independently.
Third, if teens don't know someone in the group, they can gain acceptance by hanging around for a period of time, getting to know some of the members, and becoming involved with, and accepted by, the other teens. Although accepted, this does not mean the other teens will quickly include them in what is happening socially at all times. Most likely, the doors will remain closed for a while, and they will have to find out about social events on their own. Regular members, however, are naturally "in on," or told about, parties or social gatherings.
Fourth, I know of one group where the process of acceptance into the group involved some intricate bartering. To be accepted, there had to be a sense of give and take—the new person had to first do something for the regulars; then they would do something for him. At first, it was more important to be someone they could hit up for money, cigarettes, pop, or a favor. It was also important to be cooperative and get along and not judge the group. The new person had to accept the group before its members accepted him into it.
Fifth, when a new teen comes into a teen group, there are certain things that other teens will communicate to him about the group. Older members or leaders will make very clear to the newcomer just what is and is not appropriate behavior. These peer leaders will even reprimand other teens when they do something unacceptable. These leaders help maintain the group in this way.
Bottom line: Know that becoming a member of a teen group is very difficult and time consuming, and offer loving help and encouragement at every turn. And by the way, never try to join your teen's group yourself!