This study investigated how formative assessment was perceived, experienced and accomplished by teachers and students in ten Year 7 to 10 science classrooms. The study was undertaken within and built on the findings of the Learning in Science Project (Assessment). An interpretive methodology using interviews and participant observation was employed. The study consisted of two phases. During the first phase, the teachers and at least three students of each teacher were interviewed and three classroom observations undertaken to ascertain views of formative assessment. In phase 2, case studies were developed of the formative assessment in the different classrooms. In addition, the teachers participated in eleven teacher development days, which were audio-taped and analysed. While the literature provided a definition and discussion of formative assessment relatively little research had explored student perceptions and experiences of formative assessment as an aspect of their everyday classroom life. The links between formative assessment and views of learning had received very little attention. The study provides empirical evidence that formative assessment is accomplished through situated teacher and student actions and interactions that involve the exchange, interpretation and action on information about student learning. It seems teachers and students are active and intentional participants in the process of formative assessment but not necessarily for the same purposes. Student perceptions that interactions could enhance their learning and harm their relationships with others and their view of themselves led them to consider both the possible benefit and the potential harm of disclosing their ideas to others (teachers and peers). Moreover, students indicated that whether they pursued learning or performance goals and how they perceived teacher assessment purposes influenced their purposes for and willingness to participate in assessment interactions. Cognition, affect, conation and relationships with others were experienced by the students as inextricably intertwined with their learning and the formative assessment of it. Thus, the findings indicate that formative assessment contributes to the meaning of being a student, learner, knower and peer and of being a teacher in the classroom. The findings of the study support the view that formative assessment is a sociocultural activity that may be described and is accomplished along three interdependent planes of the classroom, interpersonal and personal activity and meaning (Rogoff, 1995). On the classroom plane, formative assessment is accomplished through a process of apprenticeship and influences what it means to be a student (and a teacher). On the interpersonal plane, formative assessment is accomplished through a process of guided participation and influences what is taken and counts as school science and hence what it means to be a student (of science) in a particular classroom. It shapes how students view themselves and each other in the social milieu of the classroom. On the personal plane it shapes the language students use and how they feel about themselves as learners and knowers of school science.