Social question & answer forums offer great learning opportunities, but students need to evaluate the credibility of answers to avoid being misled by untrustworthy sources. This critical evaluation may be beyond the capabilities of students from primary and secondary school. We conducted 2 studies to assess how students from primary, secondary, and undergraduate education perceive and use 2 relevant credibility cues in forums: author's identity and evidence used to support his answer. Students didn't use these cues when they evaluated forums with a single answer (Experiment 1), but they recommended more often answers from self‐reported experts than from users with a pseudonym when multiple sources were discussed in the forum (Experiment 2). This pattern of results suggested that multiple viewpoints increase students' attention to source features in forum messages. Experiment 2 also revealed that primary school students preferred personal experience as evidence in the messages, whereas undergraduate students preferred the inclusion of documentary sources. Thus, while children mimic the adult preference for expert sources in web forums, they treat source information in a rather superficial manner. To conclude, we outline possible mechanisms to understand how credibility assessment evolves across educational levels, and discuss potential implications for the educational curriculum in information literacy.