Research efforts focused on developing "active reports" are currently underway. Active reports are designed to foster communication among teachers, students, and parents by listening to all stakeholders, using assessment information to guide teaching and learning, and to reconcile potential conflicts. Open student models can handle different views of the student. These views support different kinds of assessment information coming from a variety of sources (e.g. results from summative and formative assessments). As teachers, students, and parents interact with open student models, assessment claims (e.g. students' self-assessment, systems' and teachers' assessment of student knowledge) may evolve from unsupported claims to evidence-based arguments. Paths on this evidentiary argument space are characterized by rich interactions among sources of evidence that may challenge personal claims and improve metacognitive skills. This paper (a) presents an evidence-based approach to interacting with open student models that builds on existing research on open student models, evidentiary arguments and evidence-centered design, (b) illustrates this approach in the context of an assessment-based learning environment called Math Intervention Module (MIM), and (c) reports on a study carried out with Algebra teachers/assessment specialists aimed at evaluating the feasibility of implementing this approach in real settings.