Throughout the world, school grade structures are most variable during the early adolescent years when students can find themselves in a variety of school models. This paper investigates the impact of two popular school models in the United States (middle school and K-8) on the self-esteem and self-concept of early adolescents. Based on mixed method longitudinal research conducted over the 2004-2005 academic year, the study finds differences in levels of self-esteem amongst sixth grade students at the beginning and end of the school year, with students in K-8 buildings having higher increased levels of self-esteem when compared to students in other models. Gender analysis reveals girls are more negatively impacted by middle school environments than boys. Both quantitative and qualitative analysis reveals greater feelings of anonymity amongst middle school students and more negative attitudes toward their own social behavior. Overall results point to serious implications in school design and timing of transition for early adolescents. (Contains 1 figure, 3 tables and 1 footnote.)