Constructing validity in classroom conversations

We account for different strategies used by a group of students to talk about and assess the validity of mathematical models while working in a problem-solving task. Two main competing strategies are described, one centred in ritualized uses of well-known mathematical constructs as a means to cope with perceived didactical expectations and a second strategy centred in the assessment of the representativeness of mathematical models when accounting for the proposed empirical situation. The interactions analyzed exemplify the difficulties students and teachers experience when dealing with epistemological aspects of knowledge being constructed in classroom conversations. Our findings point to the need for research to focus on epistemological aspects of the mathematical culture of the classroom.