This paper attempts to deepen our understanding of teachers' selection and modification of mathematical tasks for their classroom instruction. In this paper, we focus on teachers' orientations and resources that subtly influence teachers' choices during their routine undertaking of task selection and modification. Interviews using stimulus…

Designing a mathematically worthwhile task is critical for promoting students' reasoning. To improve task design skills, teachers often engage in collaborative lesson planning activities such as lesson study. However, to learn from the process of lesson study, it is important for teachers to notice productively the concepts, students' confusion…