Please quit teaching students that you "just add a comma whenever you feel like the sentence needs a pause." That is a lie, and it's wrong to lie to children.
Now, if you'll excuse me, I have to go rip out all my hair and scream in desperation at the state of grammar in the world and the dismal future of grammatically correct students.
Edited to add: By popular demand, here's the link to my posts on how to do grammar simply. :)