This study explores Participatory Action Research (PAR) as a practice that promotes collaborative knowledge construction between researchers and participants. Within this framework, a PAR experience carried out for the transformation of a school in the province of Valencia (Spain) is explored. The aim is to analyse the shared construction of knowledge during the process and the changes produced through the perceptions of the educational community and the research group. From a qualitative methodology, a case study is elaborated through the analysis of documents produced during the research and ad hoc focus groups, and the data obtained are analysed following a mixed categorization. The results show that the shared construction of knowledge during PAR has led to the development of more horizontal roles and strategies between researchers and participants, and changes towards a new school model, for which the improvement of the participation of the agents involved has been key. Elements that invite reflection on the shared construction of knowledge through PAR are discussed, among which stand out the complexity of the researchers' task, the timing, the articulation of the students' voice and the relationship between the type of research carried out and the changes produced.