...Though I agree with the statements by spells, I also acknowledge that anyone not held accountable for his or her failures and given multiple do-overs for a good 12 years is probably going to be a little... uh. "Dense" is a gentler word, isn't it?
Let me qualify that a little more. While I do take radical steps like enforcing deadlines and not allowing certain assignments to be made up and reinforcing department attendance policies, I consider the first broach of any of the requirements a mistake. A mistake with varying degrees of penalty, to be sure, but a mistake borne of ignorance of how the real world functions.
When the behavior is repeated, it qualifies as stupidity, or willful error. It's the same standard I hold other folks to.
[I also make this statement now, in week 3 of the semester. By another few weeks, I will be nowhere near as gracious. The ye olde patience is already fraying.]