This research paper examines how contextual variables affect the teaching and learning of English as a Second Language (ESL) in diverse settings, specifically through observations of ESL lessons in Istanbul. It discusses the roles of teachers, linguistic choices, and sociolinguistic environments, emphasizing the impact of students' first languages and prior knowledge of English on their learning experiences. The study also highlights differences in ESL education across inner, outer, and expanding circle countries, addressing the challenges and adaptabilities necessary for effective ESL instruction.