This paper reports research from four studies of how teachers come to learn professional knowledge based on theoretical frameworks of the developmental theories of Piaget (cognitive development), Kohlberg (moral development), Loevinger (ego development), and Hunt (conceptual development). Studies proceed on the assumption that a perspective of developmental theory provides knowledge of how teachers assimilate new information and implement new teaching strategies. Findings suggest that: (1) teachers operating at higher stages of development show greater flexibility, are more able to see multiple points of view, and are more effective in supervisory interaction with preservice interns, in interpersonal interaction, and in group problem solving in collaborative action research; (2) teachers' developmental stages affect their interactions in the school setting and their involvement on collaborative research teams; and (3) collaborative action research, as a developmental education intervention, can provide the support and challenge that encourages developmental growth. Two appendices are included. The first compares and contrasts four developmental models in three stages of adult development; the second matches appropriate staff development supports and challenges with teacher developmental stage characteristics. (Contains 39 references.) (Author/LL)