Using a national dataset of the Early Childhood Longitudinal Study - Kindergarten class of 1998-1999 (ECLS-K), this study examined several issues relating to two particular social skills: work related skills (WRS) and interpersonal skills (INS). The central research questions included the overall developmental trajectories of two particular social skills from kindergarten through 5th grade, how the social skills trajectories differ among different racial groups and SES groups, how the environmental factors influence social skills' development, and the effects of social skills are on achievement growth and narrowing achievement gaps over six years and the specific effects in four time periods.

A series of three-level piecewise HLM linear growth models were created. The result provided a snapshot of how two particular social skills develop intra-individually and inter-individually across different racial and SES groups based on Bronfenbrenner's ecological framework. Although most students exhibited WRS and INS in class often at the beginning of kindergarten, on average, about half of them scored lower than the average score. The variability signified that most students were being rated as having good WRS and INS, but some other students still had lower scores and needed direction and assistance to acquire the skills through assessment or training. The growth of WRS and INS were relatively flat over time. After controlling SES, minorities had lower average WRS and INS scores at the beginning of kindergarten. No significant racial gap of social skills growth rate during the kindergarten period was found, but Asian-Pacific Islanders had significantly higher growth rate after kindergarten through 5th grade. There were significant gaps by SES in initial WRS, initial INS, and WRS growth rate during kindergarten. Children's WRS and INS scores were varied with respect to the unique contributions of parental involvement at home, parental involvement at school, parent(s)-child interaction, and class behavior.

Through use of three-level and two-level HLM techniques, the model comparison indicated that the overall WRS and INS effects on achievement growth were small on average. Although WRS and INS did not consistently further reduce the racial and SES achievement gaps, they played important roles in promoting achievement growth in different time periods. Compared to INS, WRS has a consistently positive effect on later achievement growth. Child and family characteristics better accounted for the difference in WRS and INS initial scores than schools. The findings have implications about nurturing children's social skills acquisition at an early age and enhancing their early social skills in school. Particularly, WRS was recommended as an important indicator for academic success and for a potential intervention program.