This paper describes how a cluster of nine secondary science teachers and lecturers from five schools and colleges in the United Kingdom designed and undertook small-scale action research projects as an approach to their own continuing professional development. The participating teachers identified a range of topics for investigation such as: student voice to inform curriculum planning; the use of STEM (Science Technology Engineering Mathematics) to raise student engagement and motivation in mathematics and literacy; and assessment and learning in practical work. The participants brought their research into practice either as individuals, pairs or within a team. Central to each project was the use of reflection as a primary approach to enable the teachers to self-evaluate their professional practice and gain a greater understanding of the wider contexts of teaching and learning. The key aim of establishing a cluster was to foster collaborative reflective practice and encourage a teacher-led process. Reflective practice was developed through the use of several approaches including: reflective discussions, audio reflections, a paper-based learning and evaluation tool, and an online hub. Teachers were particularly encouraged to use the latter three tools in an attempt to stimulate and structure their reflections critically about what was taking place in a given situation during their designed interventions, to identify suitable options, and to make tacit the knowledge gained about their approaches to classroom-based research. (Contains 1 figure and 1 table.)