Do prospective mathematics teachers teach who they say they are? Sonja van Putten • Gerrit Stols • Sarah Howie Ó Springer Science+Business Media Dordrecht 2014 Abstract In this case study, the professional mathematics teacher identity (PMTI) of final year mathematics education students is investigated in terms of their self-perceived and actualised identity. These prospective teachers were required to discuss and describe their own PMTI in terms of three aspects: mathematics specialisation, teaching-and- learning specialisation, and caring. Subsequently, they were observed in the classroom, where the actualisation of their PMTI was considered in terms of the same three. The participants’ perceptions of their own PMTI and the actualisation of that PMTI in the classroom were found not to be congruent. While their self-perceptions regarding their prowess as Mathematics Specialists were accurate, since this is concretely tested as part of their studies, their self-perceptions as teaching-and-learning specialists and particularly as Carers, were not verifiable in their classroom practice. Espoused theory, theory that the individual perceives as true and valid, and which may thus be seen as intrinsic to their PMTI’s, is not necessarily enacted. Keywords Professional mathematics teacher identity Á Classroom actualisation Á Theory-in-use Introduction The professional identity of the person who teaches is an essential factor in determining the success of what happens in the classroom, if we are to believe the dictum that says we teach who we are. Mathematics education in South Africa, despite the many changes in education since 1994, remains in crisis. While effort and money have been expended on improving facilities and teachers’ knowledge of mathematics, the crisis persists. Arends and Phurutse (2009) believe that a difference can be made to the state of mathematics S. van Putten (&) Á G. Stols Á S. Howie Department of Science, Mathematics and Technology Education, Faculty of Education, University of Pretoria, Groenkloof Campus, Leyds Street, Pretoria 0181, South Africa e-mail: sonja.vanputten@up.ac.za 123 J Math Teacher Educ DOI 10.1007/s10857-013-9265-0