The Australian science curriculum is intended to enable school students to develop an understanding and curiosity about the way that science can assist them in making sense of the physical and technological world. In addition to understanding and communicating scientific knowledge and using inquiry processes, students also need to develop the skills to make evidence-based decisions about socio-ecological challenges. Today's school students will need to be able to use their scientific literacy to construct arguments and make decisions about multifaceted ill-structured scientific problems (called socioscientific issues (SSI)). The aim of this research was to examine whether Year 7 (aged 11-12 years) science students located in a rural region of Australia could improve their argumentation skills following instruction in the context of water-based SSI. An experienced science teacher and her two classes of Year 7 students (n = 39) participated in the research. Using an interpretive paradigm and a case study method, quantitative (pre- and post-instruction questionnaires) and qualitative (classroom observations, lesson plans, student work samples and teacher interview) data were collected. After two consecutive lessons on argumentation about water-based SSI, it was found that the complexity of students' arguments improved significantly. Teacher strategies that contributed to the improvement included (1) creating a safe environment for students to take risks with their thinking; (2) providing multiple opportunities for students to learn and practice the language of argumentation; (3) constantly encouraging students to write down their arguments: (4) and differentiating instruction to cater for varying student abilities. It is concluded that, with extensive scaffolded teacher support, this group of students were able to understand the purpose and components of an argument and improve their written arguments.