In an educational context marked by the urgency of combating misinformation and fostering critical thinking from an early age, the ability to evaluate the credibility of information sources is becoming a core competence. This contribution focuses on a theoretical model designed to support upper primary school students (ages 9–11) in developing structured and rational criteria to assess source credibility. The model articulates two key dimensions : competence and trustworthiness, operationalized through observable cues such as expertise, reputation, incentives, and engagement.

The model was tested in a test/post-test design involving both experimental and control groups, across 29 French classrooms and over 370 students. The intervention combined conceptual teaching with guided practice. It included class discussions and exercises aimed at helping students reflect on what makes a source credible and how to justify their judgments.

Quantitative and qualitative analyses of students’ choices and written justifications show that conceptual instruction significantly improves their capacity to provide explicit and relevant criteria when evaluating sources. Following the intervention, students more frequently referred to structured dimensions such as subject-matter expertise, alignment of interest, or the source’s authority.

Beyond the effects of the intervention, the analysis of spontaneous justifications in the control groups revealed recurring reliance on cues such as access to information and social familiarity (e.g., past experience, known reputation). These findings shed light on the intuitive models that children use when judging credibility and point toward developmental trajectories in critical thinking. Understanding these initial patterns provides valuable insights for designing more effective and age-appropriate critical thinking instruction.

The proposed model offers both a conceptual lens and a practical tool to support structured reasoning about credibility at the primary level. It can help educators better assess students' evaluative thinking and scaffold metacognitive reflection during inquiry-based learning or media education activities. Overall, this study contributes to a better understanding of how young learners begin to reason about source reliability, and how these skills can be meaningfully supported in educational settings.

Keywords: Credibility, Critical thinking, Conceptual learning, Primary education.