Whereas the structure of individual differences in personal, social, and emotional attributes is well understood in adults, much less work has been done in children and adolescents. On the assessment side, numerous instruments are in use for children but they measure discordant attributes, ranging from one single factor (self-esteem; grit) to three factors (social, emotional, and academic self-efficacy) to five factors (strength and difficulties; Big Five traits). To construct a comprehensive measure for large-scale studies in Brazilian schools, Ayrton Senna Institute is developing assessments mapping socio emotional skills on the conceptual framework of the five-factor model of personality. Here we present a study of internal structure of a 162-item inventory measuring 18 facet scales, representing two conceptual levels of measurement: one assesses the child’s current identity or self-concept and the other assesses self-efficacy beliefs. These 18 facets can be organized into five broad domains, similar to the Big Five domains: E: Engaging with others, A: Amity, WO Work orientation, ER: Emotional resilience, and O: Open-mindedness. The sample consisted of more than 30,000 participants, who were between 11 and 18 years old and attended grades 6 to 12. We split the sample in two random halves. We performed exploratory factor analysis of the 18 facet scales per layer with the first half and a confirmatory factor analysis with the second half of the sample. Internal consistencies were in the range of .70 to .80 for most scales. All facet scales had their highest loading on the expected domain. A bi-factor model best represented the self-efficacy level with a general factor plus five specific factors related with each domain. A confirmatory factor analysis showed a robust and replicable structure. Discussion focuses on the contribution to socio-emotional research in education and its measurement.