Lesson study incorporating phase-based instruction using Geometer's Sketchpad and its effects on Thai students’ geometric thinking

Purpose – Geometry has, in many countries, proved to be one of the problematic topics in mathematics. The purpose of this paper is to report on a study that was carried to investigate the effects of lesson study incorporating phase-based instruction (LS-PBI) using Geometer's Sketchpad (GSP) on Thai students’ geometric thinking. Design/methodology/approach – The effectiveness of the LS-PBI using GSP within the targeted context was assessed in a quasi-experimental research approach involving three groups of mixed ability grade 7 students (12-year-olds) in one of the schools in Yala province, Thailand. These groups (Group 1: n=30, Group 2: n=28 and Group 3: n=29) were taught the topic of properties of 2D and 3D geometric shapes through phase-based instruction using GSP in turn by three different teachers. The teachers observed the lesson study teaching protocol. Data were collected using pre-test and post-test to assess students’ van Hiele level of geometric thinking. In addition, six students were selected to be observed in order to give supplementary data on their level of geometric thinking changed. Findings – Findings revealed that the LS-PBI was effective in improving students’ geometric thinking. Analysis of paired sample t-test showed that there was a significant difference in the pre-test and post-test scores in each group after each LS session. Analysis of covariance showed that there was a significant difference in the post-test scores among the three groups of students. Originality/value – The findings of this original study suggest that the LS-PBI using GSP was effective in enhancing students’ geometric thinking.