This chapter attempts to reconcile findings suggesting that early adolescence is a time during which students' motivation declines and disciplinary problems increase, and those suggesting it is a time during which youngsters endorse attitudes and values consistent with those of their social structure. The aim of the chapter is to integrate interpretations of this disparity between personal beliefs and behavior provided by scholars from differing social science disciplines. The chapter notes social psychological literature supporting the idea that behavior is affected by one's own attitudes and significant other's expectations and perceived attitudes. Developmental research shows that young teens are cognizant of the fact that their values differ from other's and that they need to vary their self-presentation to facilitate social approval. Peer approval becomes especially salient during early adolescence and public behavior is motivated by teens' desire to behave consistently with perceived peer group norms. The heightened need for peer approval, paired with the need for being seen as less dependent on adults, coincides with the transition to middle school. In this setting, young teens are especially likely to sort their social world into us versus them. Although this categorization helps youth master their expanding social world, it fosters a peer culture incompatible with the values endorsed by the most likely out-group, adult authorities. The perceptions of peer norms combined with the need to identify with a new peer collective, guide young teens public behavior, often conflicting with private values. This chapter covers research on a range of relevant behaviors, including health-compromising,achievement-related, and social behaviors. The chapter concludes with concrete suggestions for moderating the behavioral changes of young adolescents. (Contains 53 references.) (KB)