Introduction: The Strengths Scale for Adolescents (Betancourt, Andrade, González & Sánchez, 2018) is an instrument developed in Mexico that has proven reliable for assessing aspects that foster positive adolescent development, including healthy habits, avoidance of risk behaviors, school expectations, anger expression, decision-making, parental support and supervision, and peer relationships. In light of the psychosocial changes brought about by the COVID-19 pandemic, it is important to examine whether these changes are also reflected in assessment instruments.
Objective: To analyze the psychometric properties of the Strengths Scale for Adolescents (FIE-A) in high school students. Method: Instrumental study with 315 students from a public university in Jalisco, Mexico. The scale evaluates adolescents' external and internal strengths. Exploratory and confirmatory factor analyses were conducted. Results: Initial findings revealed differences from the original scale, as the subscales "Responsibility" and "Household Rules" were excluded from the models. Two models were tested: the external strengths model with 29 items showed excellent fit indices, χ²/df = 1.72, CFI = .961, SRMR = .046, RMSEA = .049 [.043, .055]. The internal strengths model with 28 items also demonstrated adequate fit indices, χ²/df = 1.85, CFI = .958, SRMR = .051, RMSEA = .052 [.046, .059]. Evidence of convergent and divergent validity, as well as measurement invariance by sex, was also found. Discussion: The scale emerges as a solid and reliable instrument for evaluating external and internal strengths in Mexican adolescents within the post-pandemic context.