The effects of non-prototype geometry instruction on 7th-grade students' conceptual learning

This study aims to examine the effects of non-prototypical geometry teaching on 7thgrade students' conceptual learning about quadrilaterals. The study employed a single- group pretest-posttest quasi-experimental design. The study was carried out with 35 7th-grade students studying in a state middle school in a province in Turkey. Data were collected using a three-stage measurement tool: open-ended questions, drawing tasks, and two-stage reasoning-based questions. The implementation process was conducted in accordance with the learning outcomes of the Ministry of National Education's 7th-grade mathematics curriculum. In addition to prototypical shapes frequently encountered by students, nonprototypical examples based on definitional properties were also included during the process. This aimed to enable students to understand the concept of quadrilateral at a conceptual level, without relying solely on visual representations. The results of the study revealed that non-prototypical teaching led to significant improvement in students' conceptual learning. Students were observed to express definitions of quadrilaterals more accurately, to recognize different shapes, and to adopt a definitional property-based approach in their drawings. Additionally, positive improvements were observed in students' ability to recognize and justify inclusionary relationships among quadrilaterals. Based on results, it can be argued that instructional strategies that emphasize the descriptive properties of geometric shapes should be employed rather than teaching based solely on visual similarities.