At the moment, I can't find any way that a teacher can force a quiz to end, which happens when students in a class do the questions, and save them, but do not submit what they have done. Could also be used as a forced closure if a teacher is manually monitoring time limits on a quiz. Would think it would be a button on the main quiz page accessible only to teachers that prompts them to submit all open attempts.

What do you think Tim? Plausible or busted?