While principals and systemic leaders have a significant role to play in leading, supporting and structuring mathematics education, their influence tends to be indirect and general. However, middle leaders such as curriculum leaders, senior teachers, and faculty heads, exercise their leadership much closer to the classroom, and as such they can have a more direct influence on the quality of teaching and learning in schools. To improve mathematics learning outcomes of student, it is crucial that educational leading is practiced by those with the greatest capacity to bring about positive practical and sustainable change--middle leaders. These school-based curriculum leaders can promote this development by engaging in forms of "Critical Participatory Action Research" that allows them to improve the quality of teaching and learning through an evidence-driven, site-based, collaborative approach.