The transition from primary to secondary school plays an important role in the academic lives of students. It affects the overall learning of students and the learning of mathematics in particular. As a student as well as a teacher, I myself have experienced difficulties in coping with the new concepts and changes in the curriculum of mathematics and its teachings. Similarly,my students have experienced the same kind of teaching and learning difficulties as I did, particularly in the first year, i.e. Grade 6oftheir secondary school education. For example, when I was a teaching in a middle school in Gilgit-Baltistan, I observed that students who were quite motivated in learning mathematics could not solve even the simplest of mathematic problems when they come in Grade 6 and remained disengaged in mathematics classes. Thus, this study aims to explore thechanging experiences of learning mathematics during the transition of students from primary school to secondary school. The study has been conducted in one of the private schools located in Karachi, Pakistan. This study employs an exploratory case study method using qualitative methods. Classroom observation, semi- structured interviews and document analysis remain the main tools of data collection. The data has beensystematicallyanalyzedin order to identify the emerging themes. The emerging themes have been interpreted on the basis of information obtained from interviews, observation and document analysis. The study reveals thatthe experience of transition into secondary school is challenging for students. This issue is significant because transition into high school coincides with the adolescent development changes- social, physical, cognitive, emotional and psychological changes. The findings of the study show that students find discontinuity in the curricular and pedagogical approaches of primary and secondary school. These include gaps between curriculum and pedagogy, teacher- student relationship, peer and teacher interaction. These gaps create certain problems for students in copingwith the new environment of the school as well in grasping advance mathematical concepts in Grade 6. This study reveals that the transition from primary to secondary school is a process and a multidimensional event in the academic lives of students. It persists as students continue to observe change due to many factors. Also, many physical, social, emotional and academic factors come together to affect the mathematic learning of students in a complex and holistic manner. This study is significant for teachers and teacher educators inPakistan, helping them to reflect upon their teaching practices, so as to identify theneeds