Classroom instructions in Hong Kong secondary school context often involve code-switching/code-mixing, with textbooks in English yet the lessons being taught in Cantonese (A variety of spoken Chinese) or a Cantonese/English mix. The code-switching/code-mixing instruction has been a common practice in Hong Kong classroom teaching. However, the Education Commission of Hong Kong considered code-switching/code-mixing instruction as the primary reason for students’ inadequate levels of English and Chinese. Therefore, the Government adopted the policy of ‘mother-tongue teaching’ to promote Chinese-medium instruction so as to reduce code-switching/code-mixing instruction. In this paper, firstly, a summary of the historical background of the Hong Kong language polices will be introduced. Secondly, the role of code-switching/code-mixing instruction in classroom teaching will be discussed by illustrating examples from a case study in a Hong Kong secondary school. Finally, the reasons behind using mixed code and its impact on student learning will be analyzed and discussed. A number of research methods were employed: questionnaire survey, student focus group interviews and classroom discourse analysis. The research findings show that students in the case study school found the use of mixed code beneficial even though the school language policy does not encourage code-switching/code-mixing instruction. We anticipate that this study will shed some light on the study of code-switching/code-mixing. Copyright © 2019 GRDS Publishing.

Background: Cantonese-English mixed code is ubiquitous in Hong Kong society, and yet using mixed code is widely perceived as improper. This paper presents evidence of mixed code being socially constructed as bad language behavior. In the education domain, an EDB guideline bans mixed code in the classroom. Teachers are encouraged to stick to Cantonese or English, depending on the school-based medium of instruction policy (i.e. EMI vs. CMI schools).
Aims or focus of discussion: This paper analyzes the major reasons why mixed code is so difficult to avoid, both inside and outside the classroom. One important factor is the 'medium-of-learning effect'. Empirical evidence will be presented to demonstrate students' cognitive dependence on English terminologies as a direct result of English medium education. The paper draws implications for classroom code-switching, which is pedagogically a valuable linguistic resource.
Arguments / comments / suggestions: The EDB guideline banning mixed code in the classroom is too rigid. Code-switching has great potential for helping the bilingual teacher to achieve context-specific teaching and learning goals like clarifying difficult concepts and reinforcing students' bilingual lexicon (e.g. melamine/三聚氰胺, financial tsunami/金融海嘯). For EMI teachers, switching to Cantonese helps maintain class discipline, build rapport and reduce social distance with students. The assumption or claim that mixed code leads to declining English or even Chinese standards is not informed by sound empirical evidence.
Conclusion: Educated Chinese Hongkongers find it difficult to resist using some English in their informal interactions with others in Cantonese, resulting in mixed code. Instead of banning mixed code indiscriminately, a more proactive and productive approach will be to conduct empirical research with a view to (a) better understanding the circumstances under which classroom code-switching is necessary, (b) identifying pedagogically