I realized that I study best when I am slightly sleep deprived.  If I get a full nights sleep (anywhere from 7-14 hours) I cannot concentrate on my homework because my mind is fully awake and so I think about multiple things all the time, get distracted, and end up getting nothing useful for school done.  But, if I get barely enough sleep (3-5 hours), then I am completely focused on my homework and get so much done because my mind is too tired to multitask/think of anything else.

Of course, this only works for like 4 days. Then I have to catch up.