Since preschool you've had a tight grip on your child's social life. You were the one making the playdates and setting up sleepovers. But now that your kid's hit middle school, the rules to the friendship game have changed. Your kid is meeting new people and growing more independent. Suddenly, you don't know the kids your son or daughter is hanging out with. And sometimes, what you do know of them worries you. What should you do when you see your child getting involved with a group of pals you think may be a bad influence? Here, experts share their advice.