The re-introduction of English Medium Instruction (EMI) to selected state and private schools of Sri Lanka in 2001 has presented several challenges to the various stakeholders within the system. This chapter investigates how these challenges have affected the students and teachers engaged in EMI in the General Certificate of Education (GCE) Advanced Level (A/L) classes of schools from the nine provinces of Sri Lanka. The study employed a mixed methods approach and used a questionnaire and semi-structured interviews as its research instruments. Sample populations for the interviews were drawn using convenience sampling. Data obtained from the open-ended section of the questionnaires and the interviews were subjected to a theme-based qualitative content analysis. The findings indicate that both the students and teachers face several challenges related to the acquisition of Academic Literacies (AL) such as the lack of basic English language proficiency on the part of both students and teachers, the students’ lack of subject knowledge, and the intensely exam-oriented teaching–learning process. Another significant finding was the diversity of views on translanguaging in EMI. Based on these findings, it is evident that although EMI has been in effect in the school system for over 20 years, there are still significant challenges to its successful implementation.