The same geometry textbook does not mean the same classroom enactment

Abstract

Textbooks are often used in classroom instruction in quite different ways, leading to potential differences in students’ opportunities to learn. This paper explores the enactment of the topic of congruence by 12 teachers using the same geometry textbook. We highlight variations in the number and nature of lessons taught or skipped, in expectations for homework, and in instructional style. For instance, teachers taught between 60 and 100 % of the lessons on congruence but often skipped content focused on unique applications. The number of minutes of homework assigned varied from 16–30 min per night to 46–60 min per night. Ten of the 12 teachers spent at least 50 % of class time each week in whole-class instruction. Only one-third used dynamic geometry software and one used no calculator or computer technology in the congruence chapters. The results provide detailed insights into differences in upper secondary teachers’ use of textbooks, an area where less research exists than at elementary or lower secondary levels.