Although South Africa is a multilingual country with 11 official languages, English dominates as the language of teaching and instruction in almost all schools. In addition to this, the Natural Sciences teachers at the school of study were cautioned not to use code-switching because the school policy states that the medium of instruction should be exclusively English. Recently, students at this school complained about teachers who had been code-switching between one or more indigenous languages and English. The objectives of this investigation, therefore, were to explore the perceptions of Grade 8 students regarding code-switching in Natural Sciences classrooms, their perceptions of the effect of code-switching on their academic achievement and also how the use of this teaching strategy influenced their respect for their teacher. Data were collected by means of a questionnaire and the findings revealed that students believed that the use of code-switching confused many students, resulting in underachievement in Natural Sciences and that they respected teachers more when they taught in English only.