This study documents an instructional methodology to teach a fundamental reasoning skill during scientific inquiry the evaluation of empirical evidence against multiple hypotheses. Using the ldquo design experiment rdquo approach with iterative cycles we developed an instructional framework that lends itself to authentic scientific inquiry by providing a nontraditional approach to three aspects of learning the activities students are engaged in during scientific inquiry the tools students use while constructing knowledge and the assessment of learning outcomes. The present article focuses on the contribution of two components of this instructional framework the effect of technology-based knowledge-representation tools and the effect of reflective assessment on learning to act and think scientifically.