Despite increasing consensus that social-emotional learning (SEL) is an important contributor to success in school and life, few tools are available for educators to assess SEL skill and to use assessment results to inform educational practice. In particular, there are no scalable, feasible, usable, and scientifically sound assessment systems that measure social-emotional comprehension, which includes mental processes enlisted to encode, interpret and reason about social and emotional information. Social-emotional comprehension includes the abilities to infer others emotions from nonverbal cues, to take others' perspectives, to solve social problems, and to enlist cognitive strategies involved in self-control. Well developed social-emotional comprehension is associated with success in school and life (McKown, Allen, Russo-Ponsaran, & Johnson, 2013; McKown, Russo-Ponsaran, Johnson, Russo, & Allen, 2015; McKown, RussoPonsaran, Allen, Johnson, & Warren-Khot, 2015). To address this need, the authors developed SELweb, a web-based assessment system for students in Kindergarten through third grade that is designed to assess four dimensions of social-emotional comprehension (Lipton and Nowicki, 2009), including emotion recognition or "Social Awareness" (Nowicki & Duke, 1994), social perspective-taking or "Social Meaning" (Happé, 1994; Wellman & Liu, 2004). Social problem-solving or "Social Reasoning" (Bauminger, Edelsztein, & Morash, 2005; Crick & Dodge, 1994), and "Self-Control," or mental processes involved in delaying gratification and controlling emotions to achieve a goal (Duckworth, 2011). This paper presents a summary of evidence from three studies of the psychometric properties of SELweb. In addition, they provide an interactive electronic demonstration of SELweb describing features that facilitate its broad use in education settings. [SREE documents are structured abstracts of SREE conference symposium, panel, and paper or poster submissions.]