The study sought to investigate the role played by language in the academic performance of science students at a high school in the Free State province, South Africa who are taught through a language different from their mother tongue. The paper reports on the decisive mantle language plays in the comprehension and subsequent scholastic performance of these Chemistry students. The study adopted a mixed method research design in which the participants were randomly assigned to either the control or experimental group using Research Randomizer. Participants in the experimental group were bestowed intervention in form of lessons and learning materials in their mother tongue. Responses were drawn from a sample of 30 tenth grade students on the role language plays in the tutelage of tenth-grade Chemistry. Data was gathered from three tests written by the participants as well as from interview responses. A paired t-test disclosed a statistically significant difference in the academic achievement of the two research groups in the posttest. The upshot affirms that the employed paradigm shift, where languages of input and output were deliberately interchanged, proved to be an indispensable instructional approach as these Chemistry students were accorded the opportunity to learn in their home language. The present research findings are in line with previous research which affirms the use of students' mother tongue as being a social practice that goes beyond the four walls of the classroom.