This study offers insights into a professional graduate programme developed at the University of Fukui (Japan) that used the lesson study approach to elevate the application of field-based reflective practise for teachers and school leaders. This paper first details the programme's structure and its school-university collaborative inquiry partnership model developed to build a sustainable platform where practices and research are integrated as teachers inquire about school-based issues. The impact of the programme and its lesson study approach is then assessed by qualitatively analysing the longitudinal reflection reports written by three graduate students enrolled as: new entrant teachers, in-service teachers, and school leaders. This study concludes by highlighting that the Fukui PGP brings a more significant commitment to HEI and the BoE and extends the application of lesson study for school changes and reforms. Internationally, it demonstrates a new systematic structure that works in institutional environments and settings where lesson study is practised to make changes in the organization. It fosters a more meaningful and critical lens to the traditional practice of lesson study.