Abstract Cantonese is the mother tongue of Macau people and mainly used in the Macau community. Hence, people in their daily lives only have little contact with English and most students feel nervous when they face a full English-language- teaching environment. In my present study, a qualitative case study, I have explored the role of code switching and how it worked in a foreign languageclassroom.Data collection included classroom observations in a Form 1 English class in a Macau Chinese-medium secondary school and interviews with the participating teacher in this English class. The collected data was categorised and coded for analysis and the interaction among the teacher and students in the class was analysed using Brown's classroom observation scheme. The findings showed that when the teacher code switched from English to Cantonese (L2 to L1),it facilitated classroom management, improved the participation of students in lecture discussion and sustained interaction among the teacher and students. In contrast, the reversed situation showed that students were mostly unwilling to express theirviewpoints because they had difficulties in understanding the teacher's English expression in this junior level. Moreover, students always had uncomfortable feelings when the teacher used English in lessons; hence, though they had their own ideas, students were likely to keep them in mind rather than present them in class during the lessons. All these findings suggested that code switching from English to Cantonese should be a tool for the teacher when students are in junior level and before proceeding to senior level. It is because code switching not only facilitates the learning of subject content, but also a way by which students reflect on different facts and viewpoints, and to create an active learning environment as a result of the

摘要 廣東話，是澳門人的母語，亦是他們在社區中最常用的語言。故此，澳門人 甚少有機會以英語來進行溝通。所以，當學生要面對一個全英語的學習環境時， 很多學生都會表現得緊張不安和不知所措。 本篇論文的主旨，是透過一個質性的個案研究，去觀察語碼轉換在外語課堂 上的角色，以及其功能。研究對象為澳門一所以中文為主要教學語言的中學， 為一個初中一年級的英語教室。將會透過課堂觀察和訪談，來收集是次研究的 所需資料。探用 Brown 的課堂觀察框架，對已分類的課堂對話、訪談內容等資 料進行分析，從而對教師與學生們在課堂上的互動情況作出討論。 研究結果發現，當教師從英語(第二語言)轉換到以廣東話(母語)授課的 時候，教師在處理課堂秩序的問題時，效能有所提昇;學生們的參與度以及與師 生之間的討論度亦有顯著的正增長。相反，當教師從廣東話轉換到英語的時候， 大部分學生會表現出一副戰戰兢兢、不太情願發表意見的樣子，原因是他們對英 語屬於初階的學習程度，當教師以英語表達，他們往往不能很清晰及全面了解學 習的內容。故此，大部分的學生都會選擇把內心的想法，悄悄地收起來，而不會 公開地在課堂上發表及討論。 根據本次研究的結果顯示，出當學生處於學習的初級階段時，建議教師以語 碼轉換，作為一個外語教學的工具，當教師從英語轉換到以廣東話授課時，不但 能夠幫助學生更明瞭教學的主要内容，而且學生將更踴躍和有自信心地提出意 見。一個師生互動的教學環境，亦因此而成功的建構出來。