Abstract: The subject of this patent is a system and method for assessing students' understanding while they are interacting with a plurality of third party educational systems. The system comprises (1) an application program interface (API) that allow any educational content provider to instrument their content with the proposed system, so that the interaction of students with the content can be tracked; (2) an inference engine that gathers and analyzes interactions across multiple students and a broad array of content, and infers both, the difficulty of each piece of content, and the understanding of each student; (3) a reporting tool for students or for educators following a group of students, expressing the level of understanding of each student and its progression over time.