Before designing, selecting, or implementing a lesson, understanding the knowledge that your students already have (or do not have) is helpful, regardless of the topic that you are teaching. When I began to teach geometric transformations to a class of tenth-grade honors geometry students, I attempted to assess their knowledge. What I learned about these students' initial understandings of geometric transformations was surprising, as well as extremely useful for planning instruction. Knowing in advance the difficulties that students may experience when learning new mathematical concepts and skills can help prepare teachers for the classroom.
Karen Hollebrand is interested in the use of technology in the learning and teaching of mathematics.