The study explored various aspects of students' social skills in an attempt to identify specific aspect that has significance in predicting their academic performance and examined the longitudinal relationship of these social skills with academic performance. The study used two models that applied advanced statistical tools to a nationally representative database of the U.S., the Early Childhood Longitudinal Study. In the first model which employed the discriminant analysis, the authors successfully classified overall performance levels of fifth graders based on their five subscales of social skills, identifying approaches to learning as the most important skill among the five. In the second model which used the profile analysis, the significant longitudinal relationship between social skills and academic achievement from kindergarten to fifth grade was confirmed; students of different achievement levels showed significantly different developmental trajectories of social skills over the six years.