Serious gaming has been regarded as one of the important student-centric learning approaches in the coming decade. However, there has been a lack of in-depth discussion of the teacher role in the course of serious gaming when it is adopted in formal schooling. The study discussed in this paper is a piece of two-cycle design-based research, involving three teachers respectively from top, middle and bottom academic banding schools in Hong Kong and their Grade 11 classes in two consecutive school years (197 students in total). In the context of formal curriculum learning and teaching, we (researchers) collaborated with the teachers (practitioners) to investigate (design, enact, analyse and redesign) what and how they should do in order to optimise their students' serious gaming process and advance the pedagogic effectiveness of serious gaming in different classroom settings.