Critical thinking skills are best taught as students participate in the scientific practice of argumentation. When engaged in scientific argumentation students are expected to engage in active listening and social collaboration through the process of negotiation and consensus building. Socioscientific issues are ideally suited for such activities. Model-Evidence-Link (MEL) diagrams provide an ideal scaffold for helping students learn to build arguments that can help them make connections between evidence and scientific explanations. In these activities students compare competing models by making plausibility judgements, then comparing how well scientific evidence supports each model. In research-based activities these scaffolds have been shown to help students better understand scientific concepts, shift their plausibility judgements, and provided insights into how students negotiation consensus through argumentation. In this article we share both the resources and instructional methods for including MEL diagrams in the middle school classroom.