Addressing socioenvironmental issues and problems related to science and technology (i.e., STSE issues and problems), particularly with increased influences from powerful groups and ideologies, requires participatory roles of citizens with critical science literacy. Hence, citizens’/youth’s collective socio political activism through science education has been advocated. Additionally, developing critical understanding of complexities of dynamic networks of power-relations that appear to influence many aspects of our societies—including professional science—seems essential to redirect science into more socially and environmentally ‘just’ forms. This chapter reports on experiences of a high-school science teacher in the UK implementing, through action research, a critical and activist science education framework in his classroom. Our research indicates that students may have initial naïve/limited understanding regarding complexity of relationships in STSE issues (i.e., reductionist, unidirectional views of cause/effect that prioritize human actors as a unified homogenous group). We argue that explicit teaching about power-relations among stakeholders, diverse human and non-human entities, and possible relationships among social, economic and environmental factors seems necessary to address students’ initial naïve/limited conceptions of complexities of STSE relationships. This would potentially facilitate taking effective and realistic socio political actions.