Understanding why teachers teach the way they do is important especially in a time of curriculum reforms. Hence, the aim of this research is to unpack the secondary school physical science teachers' beliefs on the purposes and goals of science teaching (PGST) and to check the alignment of their beliefs on PGST with constructivism. A convergent parallel mixed method design was employed. Scale and checklist were used to collect data on the teachers' beliefs. Thematic analysis of semi-structured interviews was used to explore the teachers' implementation of the science curriculum. Results revealed that while teachers agree with the basic tenet of constructivism, their beliefs on the PGST were traditional. Difficulties of implementing their constructivist ideas on teaching and learning reinforced the cultural myths. Length of teaching experience and actual classroom teaching hours were seen as significant factors in the development of beliefs, whereas familiarity of curriculum intentions correlate negatively with the development of constructivist beliefs.