Cramming is extremely useful for high-school classes, because the material really isn't that difficult, even if you have trouble with it. So it's a choice between cramming and getting an hour less of sleep, or a little more sleep and no knowledge of the subject you are being tested on.

Cramming has served well for me. Prolongued all-nighters will kill you, metaphorically and literally.
Nah, you just fall asleep somehwere along the line.