Professor, I will not be here for our next class meeting.
Is this absolutely necessary?
I tried to work something out, but I really do have to miss one class.
Will you be able to make up the work you missed?
I'm going to be doing a lot of extra reading.
Remember that I will only let you miss one class meeting per semester.
Yes, I remember.
Could you e-mail me this week as a reminder?
Sure, no problem.
Make good use of that day off ; you'll only have one this semester!