Guest Editor's Introduction
Abstract
Guest Editor's Introduction Today, formative assessment is high on policymakers' and educators' lists of instructional tools for reforming education. The logic seems impeccable and goes as follows. Formative assessment should be carried out by teachers in the service of student learning because such assessment makes clear learning goals, indexes where students are with respect to those goals, and, consequently, reveals a gap between what is and what is desired. Moreover, the logic goes, formative assessment would require teachers to use their knowledge of “the gap” to provide timely feedback to students as to how they might close that gap. In science classes, for example, argumentation provides an important feedback mechanism: Students should, science educators assume, be asked to give (often conflicting) explanations of the natural world (e.g., why things sink or float) and to justify their views based on empirical evidence. In this way, so the reasoning goes, students receive timely feedback from one another and the teacher, eliminating untenable explanations along the way. By embedding assessments that elicit students' explanations—formally within a unit, as part of a lesson plan, or as “on-the-fly” teachable moments occur—teachers would take this opportunity to close the gap in student understanding. As