The "About Me" Questionnaire (AMQ) has been used to measure components of social identity, academic self-concept and self-worth in children and adolescents in the United Kingdom and abroad. Studies have reported simple reliability statistics but a comprehensive assessment of the scale's psychometric properties has not been conducted. Confirmatory factor analysis, using a sample of 5,082 children aged 6 to 18 years from combined datasets of five cross-sectional research studies, was used to establish the psychometric soundness of the 29-item AMQ. Analysis revealed generally adequate reliability with the seven-factor structure confirmed in a replication sample. Results provide evidence of adequate psychometric properties, optimized with the omission of reverse-coded item and selected items, suggesting it is suitable for assessing social identity and academic self-concept of children and adolescents in applied settings. Tests for measurement invariance showed that the assessment of parallel constructs was strongly supported across males and females and partially supported across primary and secondary school-age groups.