This chapter examines how adolescents' self-concept beliefs are powerfully influenced by frame of reference effects, which involve students comparisons of their ability levels with those of other students in the immediate context as well as assessments of their own ability and academic accomplishments. Noting that academic self-concept is positively influenced by one's own academic accomplishments and negatively influenced by the ability levels of others in the immediate context, the chapter focuses on the big fish-little pond effect (BFLPE), providing an overview of research findings and directions that extend theoretical predictions based on the BFLPE and elaborating the implications of this research for school policies and practices. First, the chapter evaluates the effects of placement in specialized education settings for gifted students and educationally disadvantaged students. The results of these studies support BFLPE's theoretical prediction that educationally disadvantaged students have higher academic self-concepts in special education classes than in regular mixed-ability classes, whereas academically gifted students have higher academic self-concepts in regular, mixed-ability classes than specialized education settings for gifted students. Second, the chapter demonstrates the generalizability of the BFLPE by replicating this effect in two large-scale cross-cultural studies to provide further support for the external validity of the BFLPE. Last, the chapter examines Hong Kong students' self-concepts to test the effects of attending academically selective schools in the context of an Eastern collectivist culture, demonstrating that such attendance simultaneously results in a large negative contrast effect and a smaller positive assimilation effect. (Contains 82 references.) (KB)