In interdisciplinary Science, Technology, Engineering and Mathematics (STEM) education, empirical evidence is required that points to the educational contribution of mathematics. Specifically, researchers are not clear how mathematics weaves itself through the STEM education meta-discourse. This article contributes to pedagogical practices in educational institutions where STEM has been newly introduced - What are the perceptions and experiences of South African teachers on interdisciplinary STEM education, and how do mathematics and interdisciplinary STEM discourses leverage each other at schools of specialisation (SoS) in South Africa? Participant teachers were drawn from ten SoS in South Africa. SoS are STEM-dense schools in South Africa's Gauteng Province, the country's industrial and commercial hub. Interview data was collected on teachers' experiences and practices to explore the affordances of Mathematics and other STEM disciplines to influencing curriculum advancement. Situated cognition, mathematics as explorations and flow theory informed this qualitative study. In the findings, technology was regarded as raising learner motivation and mathematical achievement. Important to the study is that participants have a high regard for mathematics' role in interdisciplinary STEM education. In the study, teachers had no autonomy to pursue the STEM agenda, as they were bound to adhere to a prescribed curriculum, which hardly refers to implementation of interdisciplinary STEM education. Various recommendations are proffered, such as maintaining the positive perceptions participants have on the role of mathematics in STEM curricula. The research calls for equality and equity of all the STEM disciplines, as one STEM curricula cannot succeed without the other.