The development of middle and high school students’ concept images and hierarchical classification skills regarding quadrilaterals: A case study of the trapezoid

Previous research has examined students’ understanding of quadrilaterals, especially squares and parallelograms; however, research on students’ concept images and classification strategies regarding trapezoids remains limited. Accordingly, this study examined the development of middle and high school students’ concept images and hierarchical classification skills regarding trapezoid. The study group consisted of 251 students from middle school (5th and 8th grade) and high school (9th and 12th grade). Data were collected through a diagnostic test consisting of two forms requiring students to draw trapezoid shapes and classify trapezoids among given geometric shapes. Data were analyzed using descriptive content analysis and SPSS. The findings indicated that majority of students relied heavily on prototypical representations of trapezoid and frequently demonstrated incomplete definitions and conceptual misunderstandings. Students’ concept images and hierarchical classification skills regarding trapezoids varied across grade levels. However, most students did not reach expected level of geometric thinking throughout middle and high school.