The aim of this research is to examine the influence a Transition Year (TY) mathematics intervention has on mathematics teacher’s self-efficacy and perspectives of the topic taught in the intervention. The intervention is planned to take place over a minimum of 6 weeks consisting of 24×40 minute lessons that can be consecutively delivered or at the teacher’s discretion. As the research relates to mathematics teachers’ experiences, and their perspectives on current practice and past practice, this raises some ethical considerations for the research. The research is completed over two main phases. Phase one involves a large-scale survey identifying mathematics teachers’ current perspectives on teaching geometry, attitudes towards geometry, and their teaching methodologies for the geometry topic. Phase two will involve the design, implementation, and evaluation of a TY geometry module whereby teachers will use the topic of geometry to teach spatial reasoning.