This paper reports on South African teachers' perceptions of the educational value of new topics in a revised physical sciences high school curriculum, their content knowledge competency of these topics, and their pedagogical content knowledge in teaching them. In view of the historical inequalities of the South African education system, a focus of the study was comparison of these perceptions of teachers based at schools which are diverse in terms of location, student population, and availability of resources. We adopted a mixed methods approach in collecting and analysing data from a large-scale survey of teachers through a structured questionnaire, and followed this with interviews with 10 teachers in seeking more in-depth explanations of the findings. The study revealed that teachers at township and rural schools previously designated for black students, and suburban and city schools previously reserved for white students, have a positive perception of the new topics introduced into the revised curriculum. However, teachers at all these schools expressed uncertainly as to their content knowledge and pedagogical knowledge of the new topics.