Developing learners' critical thinking skills through inquiry-based teaching has been an important aspect of science education. This is an exploratory study aimed at investigating the practice of inquiry-based teaching in schools that use a foreign language (English) in teaching science content. To address the issue, we conducted video observations of six teachers from four community secondary schools in Iringa municipality, Tanzania, for approximately 16 h. These six teachers and 18 students were interviewed after reviewing the clips. In our video study, we noted three major barriers to students' development of critical thinking skills--teachers' knowledge and beliefs regarding the nature of scientific knowledge, a classroom culture that does not support students' development of critical thinking skills and the use of the language of instruction that is not well mastered by both teachers and students.