A problem that is still unexplored in the field of socioscientific issues (SSI) and that was explored in this study is how different students decide upon a SSI they are discussing, how their justifications change during the instruction and how they use (or not) the evidence from the learning environment to support their justifications. For the purposes of this study, two classes (12-13-year-old students) with diverse characteristics were selected from two different schools in the UK. Class A students, considered high achievers come from a white-British background. Class B students considered average achievers come from an Asian British background. The students engaged in discussions regarding a SSI (Should we kill the grey squirrel to save the red?), supported by an online learning environment. Students' written arguments, classroom discussions, and classroom observations were collected and analysed. The findings suggest that even though the two classes engaged with the same learning environment, the decisions and justifications provided by the pairs in the two classes were quite distinct. The students used the evidence from the learning environment in ways which supported their decision, and tended to ignore evidence if these contradicted their decision. Furthermore, students' justifications support the hypothesis that their decision was based on whether they identified with the actors of the issue. Implications for research include exploring how students identify with the actors of a SSI to enable us to support them overcoming their personal narratives and becoming critical evaluators of scientific knowledge.