This study was conducted to examine teachers' knowledge of teaching mathematics and writing to diverse learners, and knowledge changes that occur over time, particularly during and after formal teacher education programs. Commonplaces of teaching were articulated as subject matter, learners, learning, and context. Three measurement instruments were designed: (1) a self-administered questionnaire which explores teachers' beliefs about the commonplaces of teaching as well as procedural and propositional knowledge of mathematics and writing; (2) a structured interview built around scenarios describing various classroom situations; and (3) an observation guide to collect information on teachers' knowledge and dispositions to act in particular situations. Records of teachers' responses were recorded at three points: prior to entering a formal education program; at graduation; and at 1 year following graduation. Results of the study point out shortcomings of the research approach, particularly with respect to the thinness of data for the kinds of descriptive profiles of learners originally envisioned. The problems seem to point less to the conceptual framework of teacher reasoning and more to flaws in the research design and instruments. (Author/LL)