CLG is short for classroom (c(l)) language. (lg)
The term “classroom language” is closely associated with giving instructions, asking and answering questions about the tasks and activities in a live class, and the language that the teacher needs to succeed in classroom management. The latter entails everything that might be said or asked to maintain discipline.
Thinking aloud and commenting on what is going on (which can be anything, really) are two distinct strategies that both teachers and students may resort to either consciously or subconsciously during a live language class. What is interesting is that these are different sets not only from the speaker’s perspective, but also from that of the language of instruction, and the student’s awareness of whether the teacher can or cannot understand her native language is also a factor.
What is also notable is that using these two strategies (commenting and thinking aloud) requires knowing (learning) a fairly large number of set expressions and sentence patterns, some of which are rather high level-wise, i.e. they are likely to be not only outside the student’s ZPD, but also the teacher’s, as some teachers do not know the language they teach well.
And the last point is truly mind-boggling as it sort of explains why some teachers cannot teach using English-only: it is not because they don’t want to or the students won’t understand them. It is because they can’t because their own language is not sufficient to think aloud in it or to keep up commentary. This makes one wonder what the reason is for the stigma associated with teacher talking time. Could it be so that stigma is attached to what is hard to do to give oneself a good excuse not to do it?
When confronted with a harder task or question, some people may also swear mildly under their breath or use all sorts of exclamatory language, but their primary purpose is usually to help themselves keep their emotions under control or to stay focused, or to alleviate nagging anxiety, or to solicit support without asking for help directly. It is next to never to insult or to offend the other lesson participants or the teacher (unless we are researching teaching disruptive demotivated students).