present progressive or present perfect progressive?

[dilodi83]

Dear A and B,
how's it going? How is the course going/has the course been going since I last joined in one of our meetings?

What tense is correct?
I want to specify that I used to attend a course with A and B (They were my teachers) and now I left my town and I would like to write to them to know some info about the courses they offer... but I have some doubts about the tense I should use. I think the present perfect progressive is the correct one, but if it isn't could you tell me why?
Thanks so much for your help.

[emsr2d2]

If you used to attend a course where they were the teachers, and you want to know what has happened since you left:

How has the course been going since I left?