The Social Skills Improvement System-Rating Scales (SSIS-RS) and the Social Skills Improvement System Social and Emotional Learning Edition (SSIS SEL) are rating scales used to assess social behavior in children and adolescents. While the SSIS-RS is well-regarded and used worldwide, the SSIS SEL is establishing foothold. In the current study, we used confirmatory factor analyses to investigate the structural validity of teacher-reported social skills in both the SSIS-RS and SSIS SEL in a large sample of Norwegian first-grade students (n = 879). Our evaluation indicates that the six-factor SSIS SEL models displayed superior fit compared to the seven-factor structures of SSIS-RS in our data. Results provide evidence of (a) several excessive factor correlations in both structures, (b) a few items overlapping in content, and (c) five items that appeared statistically distinct from the overall concepts of social skills (SSIS-RS) and social and emotional competency (SSIS SEL).