With the move in the last decade toward a standards-based science curriculum, assessment has become an important part of science teaching and learning. National policies such as the No Child Left Behind Act place additional emphasis on the importance of assessment. Although many teachers have a fairly solid background in assessing end-of-term learning, and they typically engage in formative assessment in an intuitive fashion, they tend to struggle with using formative assessments that allow them to examine student learning throughout the process of teaching. One option that will allow classroom teachers to achieve this goal is the graphic organizer. Graphic organizers can be used as powerful tools for probing and analyzing student thinking and learning.