Findings of a study that investigated the meaning and assessment of student mastery in outcome-based education (OBE) and Coalition of Essential Schools (CES) classrooms are presented in this paper. Classroom observations were conducted during 1991-92 in a total of 12 10th-grade classrooms--of 4 teachers in an OBE school in Johnson City, New York, and 8 teachers in a CES program in Lancaster, Pennsylvania. Findings indicate that the student assessment practices of the OBE and CES teachers generally reflected the philosophical premises and pedagogical components of each restructuring movement. Both approaches' focuses on the student as learner and on student mastery resulted in increased student responsibility for the construction of individual knowledge and a change in the role of assessment from a separate task to an integral component of instruction. Each school combined quantitative and qualitative measurements and demonstrated a shared commitment to the beliefs that all students can learn and that learning outcomes must be explicitly stated. (26 references) (LMI)