Teachers’ ability to help students learn mathematics requires an understanding of student thinking. No less important is what teachers do with this knowledge; i.e. the nature of their decisions and actions which are based on this knowledge. Two interviews were conducted: one with two junior‐high school teachers, and the other with two eleventh grade students. The interviews consisted of two parts: (1) responding to students’ questions and ideas, and (2) reacting to teachers’ responses. The paper concentrates on teachers’ and students’ points of view on the issues of helping students to (a) reason about problem situations, and (b) construct their own knowledge.