Well, sounds like it's a matter of understanding the importance of your work. I'm sure that when it comes to other aspects of your life, like things that you really enjoy doing or taking part in that you're on point and make sure that you've got all the details and whatever covered. It's because it means more to you, school work is as it sounds to most people, boring shit no one wants to "waste time" doing. I won't go into why school is so important, or how I wish I could have gone through it differently for SO many reasons. But I will say it's something to consider. Anywho. What're some things you can do to improve.
1) Make lists: Jot down all of the different assignments you have to do in any order you need to get them done. Then, take a moment to number them from most important to least, or from hardest to easiest or vice-versa. (Personally, I would go easiest to hardest, getting the easiest done first that way by the time I get to the hard stuff, I'm already done with everything else and I can completely focus my efforts on the hard stuff)
2) Make a daily schedule for yourself: Separate your day in sections of an hour each. For example: 1 hour spent on studying, next hour clean your room (or whatever else you can think of doing), next hour go back to studying, next hour take a break and do whatever you want, next hour hit the books again, etc. The idea is that when you break up your day, you give yourself breathing room, not only that, but whatever you've studied already is being processed by your subconscious while you're doing other tasks, which helps in retaining and understanding the information. You'll find yourself thinkin about the subject material while you're doing those other things too. Not the entire time, but at moments.
3) STAY FOCUSED: Another reason to break up the day is to really devote yourself to whatever you're doing on that hour. Work hard and smart, don't worry about other things, remove any distractions (careful not to think about what's distracting you though, that wastes time. Instead, just work and when you notice anything annoying you while you're tryin to do what you have to do, stop it, or remove it, then get back to work, repeating if necessary)
That's mainly it, that's what works for me, and the results are seriously mind blowing. You'll find yourself more enthusiastic to get the work done, and you managed to get other things done in the process. Hope this helps. And if you truly don't have time for the hour to hour thing, just let me know, there are things you can do for that as well. But basically it's all about time management. But again, I've got some tricks for that too. Hope this helps.