As the dissertation is almost finished I thought I had better refresh the blog.
I actually ended up doing a study of just one lesson at my university as the language school teacher didn't have the time to do it.
The group were given a questionnaire asking about learning styles and 7 self-reported skill levels, such as fluency, grammar, reading etc, then filmed and recorded the lesson, transcribed 2 1/2 hours (which was a hell of a task!) analysed number of student utterances and teacher questions and st answers. I also looked at grouping in the lesson.
Gardner's Multiple Intelligences theories was used with the self-reported questions in differentiating, Bloom's taxonomies in question level and Vygotsky's Zone of Proximal Development to consider grouping.
My conclusion is going to be that the teacher did a fairly good job of differentiating without knowing anything about differentiation!