Always leave a student with away out, don’t push them to the wall. Avoid phrases like “do this this instant!” Instead, say something to the effect of “I would appreciate it if you could have this done in five or ten minutes. Could you do that for me?” This will allow them to make a choice and feel as though the have some control in the situation. Additionally, if the situation is tense, the five to ten minutes will allow the student to calm down, think rationally and make the right decision.