The introduction of Computing to the national curriculum in England has led to a situation where in-service teachers need to develop subject knowledge and pedagogical expertise in computer science, which presents a significant challenge. Professional learning opportunities can support this; these may be most effective when situated in the teachers' own working practices. This article describes a project to support Computing teachers in developing pedagogical skills by carrying out classroom-based research in their schools. A group of 22 primary (Grades K-5) and secondary (Grades 6-10) teachers from schools across England planned, designed, and implemented research projects either individually or in small groups, supported by a team of university colleagues. Inter and intra group progress was shared online and face-to-face within a distributed community of inquiry. Data collection included surveys, video data, and the projects completed by the teachers. The findings from the project are analysed using Clarke and Hollingsworth's Interconnected Model of Teacher Professional Growth (IMTPG), which enables an identification and exploration of teacher change. Results of the analysis demonstrate that the approach can foster "growth networks"--the construct used within IMTPG to indicate teacher change which is likely to be sustained and fundamental to teachers' understanding. The individual nature of this change indicates that the approach supports personal change related to each teacher's specific situation. Although there is a huge literature on action research as part of teacher professional learning, we believe this to be the first time this has been carried out in the context of computer science education. We conclude by critically reflecting on the lessons that we have learned in leading this project.