Say it in Kiswahili: The Impact of English as the Medium of Instruction on Students' Comprehension and Expression in Tertiary Education

The challenge of using and understanding English Language by Kiswahili L1 speaking learners is dominant in Tanzania. Having English as a foreign language (i.e. not largely spoken at social contexts) make it not accessible to many. Moreover, in Tanzania research shows that English being the medium of instructions to all subjects (except Kiswahili, Chinese, French, Arabic, and Historia ya Tanzania) from secondary schools to universities limit these learners from understanding academic content, expressing themselves in written and spoken forms, and succeeding in exams. The present study aimed to explore how the use of English as the language of instruction affects tertiary students' written and oral expression skills, including their ability to articulate complex ideas and engage in academic discourse compared to Kiswahili. This case study research involved 83 tertiary students who were sampled purposively from five tertiary institutions. Open-ended questionnaires were used to collect data on the tertiary students’ perception of the use of English as the LoI compared to Kiswahili. Audio-recorded class tasks (oral presentation and note taking) were used to collect data on the tertiary students’ performance differences on the use of English as a LoI compared to Kiswahili, and the learning difficulties caused by the use of English as the LoI on tertiary students' comprehension and expression. Guided by the Cognitive Theory of Learning and the Cummins’ Linguistic Interdependence Theory, data of the present study were analysed using descriptive method, thematic analysis, and ACTFL Proficiency Guideline. The study revealed that Kiswahili native-speaking tertiary students have low English proficiency, making them more confident and comfortable communicating in Kiswahili than English, which leads to different language-related learning difficulties. The study recommends bilingual teaching, additional language support, and considering the use of Kiswahli in academic settings to enhance students’ comprehension and reduce the adverse impact of English as the language of instruction.