Abstract This study aims to analyze the perceptions of Spanish secondary school teachers in the fields of social and experimental sciences (n = 215) regarding the formative relevance of argumentative competence in the context of citizenship education. It also seeks to provide a psychometric instrument supported by robust empirical evidence of reliability and validity to achieve this goal. Based on a non-experimental, cross-sectional design, the AASES (Assessment of Argumentation in Social and Experimental Sciences) instrument,—developed ad hoc,—is administered to identify the potential relationship of sociodemographic factors with the theoretical subconstructs it comprises, the statistical association between age, origin, and gender, and the mediating role of gender in the relationship between age/place of origin and the defined latent factors, and the existence of significant differences among sociodemographic groups. The results indicate that, although a statistical association between age and gender was observed, the mediating role of gender in the relationship between age, origin, and the latent factors cannot be confirmed. SEM analyses showed that none of the sociodemographic predictors (age, origin, and gender) exert statistically significant direct or mediating effects on the latent factors. Furthermore, the comparative analyses complement the model by indicating that perceptions vary moderately by gender and age, even though these variables do not explain the latent factors in the SEM. Indeed, the analysis of variance revealed significant differences in the Critical and Ethical Skills dimension based on these two factors, with higher scores among male teachers and in the oldest age group, as well as increasing trends, with age, in the perceived importance of argumentation for the development and acquisition of critical thinking skills, informed decision-making, and ethical discussion. The findings highlight the need to incorporate specific spaces within the curriculum and teacher education programs to foster argumentative competencies and informed engagement with controversial socio-scientific issues, taking into account sociodemographic variables as influential factors in the educational process.