This approach to professional development is not about telling teachers what and how they should teach. It is about empowering teachers to make their own decisions about what needs to be taught through classroom research to discover critical aspects of objects of learning for their students. Empowering teachers in this way has been identified as the ‘soul’ of Japanese Lesson Study (Cheng, 2019) to which Stigler and Hiebert (1999) attribute the success of the Japanese education system. Without teacher involvement at the development stage, top- down curriculum development is almost bound to fail. With reference to cases of collaborative professional development to improve learning outcomes for students in Brunei Darussalam, this presentation takes care to include the teachers’ voices. They are the subjects and not the objects of research into their own professional development. The cases reveal the need to remove the effect of washback from assessment of a centralised national curriculum by empowering teachers to participate in the design of that curriculum.