13th International Congress on Mathematical Education Hamburg, 24-31 July 2016 1 - 1 THE LESSONSKETCH ENVIRONMENT: A PLATFORM FOR ONLINE TEACHER EDUCATION AND RESEARCH ON TEACHING Justin Dimmel Pat Herbst Umut Gürsel Amanda Milewski Ander Erickson University of Maine University of Michigan University of Michigan University of Michigan University of Michigan Records of what takes place in mathematics classrooms are indispensable in mathematics teacher education and in research on mathematics teaching. We describe here the LessonSketch environment, an online platform for creating and analyzing representations of mathematics classrooms. We describe the authoring and analytic tools of LessonSketch with a focus on how they have been specifically developed for representing the activity that takes place in mathematics classrooms. Following the description of the environment and its tools, we review how LessonSketch has been used for secondary mathematics teacher education and for research on secondary mathematics teaching. INTRODUCTION LessonSketch (www.lessonsketch.org; Herbst, Chazan, & Chieu, 2015) is an online platform where users can create, view, annotate, and discuss records of practice. The environment was designed to represent the mathematics-specific activity that unfolds in secondary mathematics classrooms. LessonSketch includes Depict, which is a tool for authoring classroom scenarios; Annotate, a tool for adding comments to or highlighting segments of representations of instruction; and Plan, a tool for arranging representations of instruction into multimedia questionnaires that users interact with multimodally online. The environment also contains various collections where representations of practice can be archived. The purpose of the LessonSketch environment is to provide a platform where the instructional practices of mathematics teaching can be used for research and practice- based teacher education. AUTHORING REPRESENTATIONS The LessonSketch environment includes Depict, a storyboarding tool that uses a customizable graphic language (Herbst, Chazan, Chen, Chieu, & Weiss, 2011) in a drag-and-drop interface. A storyboard, or depiction, is a collection of discrete classroom scenes that are represented through modifying a set of non-descript characters (e.g., teachers, students) and classroom resources (e.g., furniture). The characters are non-descript in the sense that they do not represent any particular type of student or teacher and can be made to be visually identical apart from differences in facial expressions, clothing, or hand or head position. Figure 1 below has an example of what the characters look like in a scene from a depiction. Using Depict, a storyboard author can narrate the action and dialogue that takes place in a classroom, frame-by-frame. Depict provides a relatively small set of building blocks that can be modified and combined to create representations of a wide range of classroom activity. The environment provides classroom templates that are populated with students, teachers, and furniture