I have noticed that students are getting up during class and leaving with increasing frequency.  This is disruptive, rude, and disrespectful behavior.  That is probably not your intention, but that is how it is perceived.  I feel it is part of my job to bring that fact to your attention. 

There are, of course,  situations where you will need to leave class early.  In that case let the instructor know ahead of time or at least sit in the back of the classroom and when you leave do so quietly and inconspicuously.