I'm in high school too and I have those days and I'd say yeah, 1-2 hours is definitely worth it but if it gets to about 30 minutes before you have to wake up or less, it's better to just stay up and drink lots of energy drinks. If you go to sleep at that point you'll just wake up more tired than you were before falling asleep. But don't stay up that late if you have responsibilities after school. Unless the assignment is a big part of your grade it's not worth it, because by the time school is out you'll be ready for a nap. And don't do it 2 days in a row because when i do, i get these weird times where i'm dreaming with my eyes open or i can't concentrate or see straight. Also (if necessary) you could sleep during lunch and have a friend wake you up when it's over. I usually get more than 6 hours of sleep though. That's healthiest. But when it comes to finals week or if you need extra credit or makeup work it's best to do it during lunch, and right after you get home, and then hopefully you won't always be up that late.