摘要
In response to global competition and Taiwan’s 2030 Bilingual Policy, English Medium Instruction (EMI) has started migrating from higher education to secondary education in Taiwan. Research on EMI effectiveness is mostly based in university settings; less is known about the EMI learning outcomes and pedagogies in high school scenarios. The present study compares the learning outcomes of an online EMI and a non-EMI math course in a senior high school through a quasi-experimental design and further examines the support for subject vocabulary on students’ learning performance in EMI classes. The initial statistical results show no significant difference between the learning outcomes of the EMI and non-EMI classes. Further examination of the instructional design of the EMI course, together with student feedback, suggests that math vocabulary instruction, including matching games and authentic tasks, positively affects the students’ motivation, and engagement. The results indicate that contextualized vocabulary learning benefits both the subject and language learning, including the authentic tasks that allow students to use the vocabulary in context. Pedagogical implications drawn from this study emphasize the importance of vocabulary support for EMI, and recommend integrating vocabulary support as either an integral or extra component in high school EMI curriculum. © 2024 International Journal of TESOL Studies.