In this article, we propose that guiding teachers to examine the regulative/discursive norms of school mathematics with tools derived from social semiotics can serve two related goals: (1) to deconstruct the "math is math period!" disposition in prospective teachers by promoting their critical understanding of the symbolic domination work they often unknowingly perform and (2) to reconstruct a more socio-political disposition by equipping them with tools for decoding the dominant discursive practices of school mathematics. After reviewing research on the social semiotics of mathematics education, we discuss two sample teacher education tasks designed with the above goals in mind.