This paper reports on case studies of eight student teachers in Andalusia (Spain) intended to identify and understand the development of their pedagogical approach and the factors affecting their socialization processes. Five factors affecting the socialization of students during practical training were evident in all the cases. These factors were: the pressures of school and classroom culture, feelings of dependence and insecurity arising from the provisional nature of their position, lack of theoretical/practical alternatives to the methods being used in their practicum situation, the evaluation process, and the relationship between the tutor and the student teacher. In the case studies investigated, the interventions of the university supervisor did not offer opportunities or conceptual instruments for analyzing the educational value of the practical work. With regard to the practicum, a marked discrepancy was evident between the opinions of student teachers and those of researchers. Students considered the period of practical work the most important part of their training curriculum. The case studies and other related research indicate, however, that indiscriminate and ill-prepared practical training, without appropriate links between theory and practice, often leads to a rapid and premature socialization linked with undesirable and outdated methods of working and conceiving educational activity. (Contains 13 references.) (ND)