Explaining scale in geography: An investigation of disciplinary and pedagogical expertise

Scale is an important part of geographic thinking but it is a difficult concept for students to learn and for teachers to teach because it is a deeply embedded and multilayered concept in the discipline of geography. Scale has come into the K–12 sphere of geography education because it has been identified as one of the five central goals of the Advanced Placement (AP) Human Geography course. The purpose of this study was to investigate the impact that differences in the disciplinary and pedagogical knowledge of three groups of teachers would have on the design of instruction for teaching scale in AP Human Geography. A total of 36 participants (12 geography professors, 12 AP Human Geography teachers, and 12 pre-service secondary social studies teachers) completed three tasks. Participants organized ten mini-geography case studies into piles according to an underlying geographic concept, constructed a 1–2 day lesson plan teaching “the most important aspect of scale” for AP Human Geography students to learn, and selected, ordered, and discussed use of the mini-geography case studies as examples for teaching scale. Geography professors had significantly greater disciplinary knowledge of human geography and scale in particular than AP teachers and pre-service teachers. AP teachers had significantly greater pedagogical content knowledge for constructing effective instructional explanations to teach scale to students than either professors or pre-service teachers. AP teachers also had significantly more awareness of the student during their interview than professors. Professors tended to “lecture” students about the core principles and conditions of use for scale and pre-service teachers talked about the logistics of implementing their lesson and continually prompted themselves to think about student background knowledge. Scale tended to be less visible to participants when embedded in an authentic geographic context irrespective of the amount of formal geography background participants' possessed. When scale was prompted, AP teachers had a significantly greater intention of flagging scale to their students than either professors or pre-service teachers. Also suggested was the link between variation in AP teacher performance and disciplinary knowledge of scale as a metasystem that needs to be flagged throughout the AP Human Geography course.