This article draws upon the experiences of a five-year government-funded university–school partnership project known as the Partnership for Improvement of Learning and Teaching (PILT) (2004–09), aimed at supporting teachers through improving their teaching quality and enhancing their professional growth in key learning areas – particularly mathematics, education and personal, social and humanities education – and initial experience of another completed project, the School Improvement Project for Early Childhood Education (SIP-ECE). The article first describes the rationale and operation of the PILT and SIP-ECE, respectively, and then explores the application of a 4-P (problem clarification, planning, programme action and progress evaluation) action learning approach to the improvement of subject teaching practice. This is followed, through case studies, by an exploration of teachers' own perceptions and university partners' perceptions of professional development and instructional improvement through the project. The final part of the article refers to Western concepts of professional development and university–school partnership, and suggests ways forward for school-based teacher development and instructional improvement in Hong Kong. Copyright © 2012 by the Editor.