In school or during whichever extracurriculars require additional time, make note of everything you need to do for it on each and every day in your agenda. For instance, if you have a chemistry project due the following Friday, write to plan it Monday, to buy supplies Tuesday, to do half of the assembly Wednesday, and to finish the assembly Thursday. Though it may take up more space, this avoids an all-nighter to finish major projects and assignments. This especially works for studying for major exams (study in increments days ahead of time to save time the night before and not cram and become sleep-deprived) and assignments due long in the future (do a little work each weekend for instance). 

Look at everything you have on your agenda. If it is just school work, be sure to add other activities you need to do that night (e.g. walk the dog, go to the gym, practice the cello). Then, figure out how long each thing will take you to complete; this only needs to take a minute or two. If you would like to write down times for each activity, go for it; or, you can recall your math homework needs an hour and your physics sheet needs 20 minutes. By now, hopefully, you still have 5-6 hours before bed time which in theory should be plenty of time to accomplish everything. 

One of the best tips here: do your homework to study. If you have an algebra quiz on Tuesday and your homework is due that class period, great! do the assigned problems as your studying (or in addition to it). If you have a biology exam on Wednesday but your homework isn't due until Friday, doesn't matter use the practice problems to prepare for the exam. Two birds one stone and this will save you a tremendous amount of time while being the same, if not more, amount effective (provided the content is the comparable).

Even when you follow these steps to a tee, they may not work out on days where certain assignments take significantly longer than anticipated. It's okay, we adapt. In your agenda or re-written to-do list, star the assignments that are due the next day, are for a test the next day, or are just generally important. When you notice time is fleeting, do those first. 

Teenagers need 8-10 hours per night on average. No, you are not the exception. Sleep deprivation impairs memory and cognitive function. With chronic sleep-deprivation, you will also be more anxious; sleep-deprivation is stress-inducing for your body. When you study rather than sleeping, you cannot properly retain the information and you may even fall asleep during the exam. For example, in freshman year, a friend of mine stayed up till 4 am studying for an exam, only to get a 40 on it. If she had reviewed less and got an adequate amount of sleep, she would have better retained whatever she read rather than studying for hours and forgetting it; at the very least, she could've made better guessing decisions.