Purpose. The purpose of this paper is to clarify the validity of the Interaction Rating Scale Advanced (IRSA) as an evidence-based practical index of social skills. Methods. The participants in our study were 17 high school students. The participants completed the five-minute interaction session and were observed using the IRSA. Their teacher evaluated their social competence based on regular observation in school. Results. The results indicated the high correlation between IRSA scores and teacher's practical evaluation. IRSA can measure social competence with high validity. Conclusion. The IRSA provides further evidence of the fact that in order to study social competence development, it is important to evaluate various features of the interaction like IRSA subscales.