Within the social nature of teaching and learning mathematics, language can be viewed as the principal resource for making meaning in the classroom. However, research has shown that facilitating classroom discourse can be a key challenge for prospective teachers. In response to this concern, my dissertation offers case studies of three secondary mathematics student teachers as they facilitated small-group problem-solving activities. Through this work, I aim to uncover not only what meanings the student teachers made in discourse with algebra students, but also how those meanings were made. This is to understand the why a text means what it does, and why it is valued as it is (Halliday, 1994). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]