In this article we describe the results of a special final course, at the main teachers' college in Mexico, which had two related main objectives: one was to find out the Mathematical Knowledge for Teaching (MKT) held by student teachers (ST) at the end of their instructional preparation. The other was to discern ways to improve this knowledge and to document the changes observed. In teachers' colleges in Mexico, math contents and pedagogical ideas are taught separately, so we aimed to help student teachers to integrate these. The analysis showed that their knowledge is mainly instrumental but that through discussions and reflection about the main issues, they were able fairly quickly to attain a significant improvement in all the contents included. Moreover, they also showed changes on some of their views about math and its teaching. [For the complete proceedings, see ED585874.]