This paper analyzes the effect and impact that teachers' practicum experiences in Early Childhood Education and Primary Education bachelor's degrees generate on the people and institutions involved (schools and Faculties of education) in the opinion of students, tutors and institutional leaders. From a qualitative and descriptive perspective, we carried out a multiple case study in 16 schools that host trainee students from the Universitat Autònoma de Barcelona and the Universitat de Lleida, in their third and fourth course of their bachelor's degree. The data collection process combined semi-structured interviews (N = 102) with coordinators, students and tutors from schools and faculties of both bachelor's degrees, analysis of 28 students' practicum reports and 2 focus groups with institutional leaders for contrasting our findings. The data analysis consists of a mixed codification and categorization process. Results show that the practicum contributes to the development of student capacities and has a positive effect on the professional development of school and faculty supervisors. In contrast, the effect that the practicum could generate in the institutions involved is lower than might be expected. The practicum generates work dynamics that cause an impact mainly on the class level, but not on the whole school; in faculties, it generates an indirect repercussion through the faculty tutors, as long as they update the contents they teach; and professional relationships established by supervisors do not generate synergies between institutions.