In K-12 education, formative assessment is a pedagogical process gathering momentum among researchers and practitioners. It has become a common theme at educational conferences, a key Organisation for Economic Co-operation and Development (OECD) research theme since 2002 and the subject of increasingly frequent requests for government funding in various nations around the world. A school that implements formative assessment reform is engaged in a dynamic process that links instruction and curriculum with assessment in order to support individual learning in the social setting of the classroom. Formative assessment is described, with the elements and principles that direct the assessment process delineated. The importance of high-quality interactions to formative assessment is considered, as well as an evaluation of the theories that form the basis for the formative assessment process. (Contains 1 figure.)