Teachers do not directly implement new teaching materials, but rather adapt them. For changing teaching practice, research requires more insights into these adaptions. This study draws on the Theory of Instrumental Genesis to describe the ways teachers adopt the percentage bar model to create different learning opportunities. The results of the exploratory case study show two fundamentally different utilization schemes of the percentage bar model employed by teachers in the classroom. The utilization scheme of Partitioning and Counting creates learning opportunities for the conceptual core of percentages and proportional reasoning, whereas the utilization scheme of Mirror Movement only addresses scaling. Implications include that researchers need to pay close attention to the utilizations of new teaching materials, and teacher educators need to provide new routines along with new materials.
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.