Teaching English as a second language in Hong Kong has been undergoing considerable change in the last two decades, from the Oral-structural Approach to the Communicative Approach, and more recently the Task-based teaching and learning. Hong Kong ESL teachers are having to rethink classroom strategies. This poses a particular problem for student teachers who have limited understanding of what this involves. Moreover, the only experience they can rely on is their own as pupils, and this has been rendered largely irrelevant at a time when the standard of English in schools in Hong Kong is said to have been declining. The speaker explores how eight student teachers who consider themselves linguistically deficient develop their professional knowledge in learning to teach ESL. Results show that the thinking, knowledge and practices of these student teachers who entered teacher education with an 'empty disk' did change critically on the course. Implications are drawn for developing TESL programmes for teaching candidates who are less competent in English.