By now, there is substantial evidence that the mathematics students pick up in the their lessons can be considerably different from the mathematics teachers to convey. Students infer way of doing and thinking about mathematics from the way their teachers do and talk mathematics in class, from their textbooks, from the way their work is being assessed. The gap between what teachers convey explicetly and what they convey implicitly, sometimes referred to as the implicit curriculum, is often difficult to detect and articulate. We do not understand well what are the nature and characteristics of the implicit curriculum, how it varies across grade levels, mathematical areas or different teachers, and how it impacts student learning, particularly during transition periods, like the secondary-tertiary transition. A central question is how can we support teachers and lecturers towards more conscious and informed decisions about the implicit curriculum in their lessons?