This paper outlines a research project which aims to support the pedagogical practices of Mathematics teachers in socioeconomically underprivileged post-primary schools. In Ireland, the socioeconomic background of a student continues to determine how likely they are to experience high-quality post-primary education and make the transition to further or higher education. This is particularly relevant in mathematics, which remains a gateway subject in accessing third-level education. This research aims to address such inequity by supporting teachers to incorporate student-centred practices in their mathematics pedagogy. The project is undertaken in two phases: First, case studies of high-quality mathematics teaching and learning will be conducted in four schools. The findings from the case studies will inform the design of an intervention, which will involve 10 pilot schools across Ireland in the 2023-24 academic year. The research team (and research Mathematicians) will collaborate with the schools and support the teachers to reflect on and reform their teaching by engaging in school-based Lesson Study. This paper provides an outline of the project and initial findings which will contribute to research on the teaching and learning of mathematics in Ireland.