Marginalization, widely associated with poverty, inequality, and underdevelopment restricts access to resources, limits freedom of choice, inhibits the development of individual capabilities, and makes it challenging to escape from marginalized circumstances. We examine marginality in mathematics teaching and its complexities in the tightly centralized educational system in the Philippines by identifying the different situations that contribute to how mathematics teachers can be excluded from certain educational practices that would normally fall within their mandate as professional teachers. Adopting Gatzweiler and Baumüller's (Marginality: Addressing the nexus of poverty, exclusion and ecology, Springer:27-40, 2014) framework, we interviewed 15 mathematics teachers from different geographical locations around the country. We identified and organized the drivers of marginality into biophysical and societal causal clusters that enable or constrain teachers to act as professionals. Biophysical causal clusters include mathematics curriculum and mathematics assessments among others while societal causal clusters include various directives, interpretations, and realities surrounding the biophysical causal clusters. Discussions about the complexities brought about by these clusters and how teachers act or respond as they navigate around them are highlighted. Recommendations for concrete de-marginalization actions are offered.