The main purpose of this thesis is to investigate how future pre- and primary school mathematics teachers change their approaches to mathematics and mathematics education during their subject studies, and also how this view has affected their teaching of mathematics after graduation. A qualitative interview method was used in combination with observations, notes, sound recordings, video recorded mathematics classes and materials produced by the teacher in order to answer the research questions. The research was carried out in two parts. The institutional theory has been used as theoretical framework throughout. This perspective was supplemented by a design theoretical perspective in part two. In the first investigation it became clear that the language used by the students is under change, and that they use terms from the national curriculum as well as the aims of the programme syllabus when they discuss mathematics teaching. The results from the observations later show that four out of five of the teachers have a clear connection to the sort of teaching they said they want to conduct, in that there is a clear relationship between the sort of teaching that they claim to perform and the sort of teaching they actually perform. From the overall results, it is apparent that teachers one year after graduation describe that they feel well prepared for teaching mathematics in preschool and primary school. This is interesting in the light of their dissatisfaction with the limited emphasis on concrete recommendations and "tips" directly after their graduation. In fact, the teachers said that in practice it turned out that their education provided a more stable and secure foundation than they described it to be shortly after having completed their mathematics studies. They say that during their education they developed knowledge and skills that enabled them to be better prepared for their future work roles than they believed themselves likely to become.