Using a new method to measure identity, we attempt to capture salient identities of young children developing into "good students." Using a nationally representative sample of American kindergarteners who advance to the first grade, derived from the Early Childhood Longitudinal Study, we examine identities based on socio-economic status, motor skills and weight that affect school performance as measured by both cognitive and non-cognitive skill assessments. Results reveal that identities derived from socio-economic status and motor skills are positively linked to school performance outcomes, and parents of first graders negatively link identities derived from body weight to first graders' non-cognitive skills. Our findings have implications for policies that concentrate on cognitive skills and ignore work habits when evaluating performance. We discuss the importance of linking identity development to both types of skills because American teachers and parents, unlike teachers and parents in East Asia, do not recognize the need to stress ability and effort equally when assessing schooling. We also interpret the meaning of our results for the No Child Left Behind Policy. (Contains 8 tables and 2 notes.)