I've been working on this topic, too... like your students, students
(and teachers as well) in Hong Kong do a lot of code-switching (between
Cantonese and English), and this has been made (in the public and
government discourses) a scapegoat for the language "problems" that
HK students are supposed to be having... and now code-switching is
"officially" banned in all classrooms in HK... but the reality speaks
otherwise... (and the official banning has created lots of dilemmas for
teachers... SIGH...!)
I use a conversation analytic framework; Peter Auer's book: BILINGUAL
CONVERSATIONS (John Benjamins) is helpful in outlining how conversation
analysis techniques can be used for doing this kind of research.
Marilyn Martin-Jones at the Lingusitics Dept. of the Lancaster
University, England does a lot of code-switching research in British
classrooms... she has an article reviewing the literature:
"Code-switching in the classroom: Two decades of research"
In G. Ludi, L. Milroy & P. Muysken (Eds.) ONE SPEAKER, TWO LANGUAGES:
CROSS-DISCIPLINARY PERSPECTIVES ON CODE-SWITCHING. Cambridge U. Press.
Monica Heller in the Franco-Ontarian Centre at OISE here does
code-switching research with French-Canadian students...
There will be a special issue of _ Linguistics and Educatio _n specially
devoted to bilingual classroom practices in multi-lingual settings; it
will come out probably some time next year. (I'll have an article in it,
"Bilingualism or Linguistic Segregation: Symbolic Domination, Resistance
and Code-Switching in Hong Kong Classrooms"; if you're interested in it,
I can e-mail it to you).
All the best!
Angel