Abstract
How can basic research on mathematics instruction contribute to instructional
improvement? In our research on the practical rationality of geometry teaching we describe
existing instruction and examine how existing instruction responds to perturbations. In this
talk I consider the proposal that geometry instruction could be improved by infusing it with
activities where students use representations of figures to model their experiences with
shape and space and I show how our basic research on high school geometry instruction
informs the implementing and monitoring of such modeling perspective. I argue that for
mathematics education research on instruction to contribute to improvements that teachers
can use in their daily work our theories of teaching need to be mathematics-specific.