Occupational socialization in schools is a known factor counteracting attempts at educating innovative teachers. In this study, findings are reported from a longitudinal study conducted among 357 students, 128 cooperating teachers, and 31 university supervisors from 24 graduate teacher education programs. Quantitative survey data as well as in-depth qualitative data were collected over a period of 4.5 years. Development of teaching competence was followed from candidates' enrollment until their third year as in-service teachers. Occupational socialization in schools was demonstrated to have a considerable influence on the development of graduates' in-service competence. However, evidence was also produced for an impact of specific characteristics of the teacher education programs studied involving the integration of practical experience and theoretical study. Implications of these findings for the design of teacher education programs and the conduct of teacher education research are discussed. (Contains 2 figures, 9 tables, and 5 notes.)