This paper explores the experiences of 37 physical science high school teachers who participated in a professional development (PD) programme coordinated by three Experimento multipliers. The Experimento programme is a Siemens Stiftung international educational programme aimed at providing didactic and methodological approaches to classroom experiments using an inquiry-based approach to science education. Experimento multipliers are the facilitators of the PD. The main data source comprised teacher interviews, school observation visits on classroom activities using the Experimento 10+ box and the facilitators' field notes. Findings suggest that there is a shift from the traditional approaches of science teaching to the implementation of inquiry-based teaching which was encouraged by the gradual formation of a community of practice, a reconceptualization of the term "practical activities" as prescribed by the CAPS document, and the need for experiments which facilitate action-oriented teaching. The discussion highlights the implications of these findings for the practicing teachers' professional development and the problems of linking theory with practice in such development. The study recommends more interventions throughout the year to enable teachers to improve their skills of implementing inquiry-based teaching, content knowledge and science pedagogy as evidenced by analysis of their summative evaluation of the intervention.