Qualitative methods were used to study: (1) the effect of engaging in a mathematics teaching experience in an alternative high school program, the Transcend program, on preservice teachers' beliefs; and (2) the effects of a guided preservice teaching experience on at-risk learners' beliefs, self-concepts, and mathematical development. Five secondary preservice mathematics teachers and five at-risk learners were the subjects of the study. Researchers used observations, videotaped classes, interviews, and a mathematics assessment to gather information about the effects of the alternative mathematics program. Case studies of three preservice teachers and two learners are presented to illustrate their development and interactions. There were changes in the self-concepts of the teachers, their perceptions of at-risk learners, and their instructional practices, although many of their beliefs remained unchanged. Students experienced learning gains, especially with regard to increased mathematical self-concept. Transcend appears to have provided both teachers and learners with a unique environment to enhance mathematics teaching and learning. (Contains 27 references.) (SLD)