I know this might seem odd, but it's really alright to ask your teacher any questions you have about something. It doesn't make you stupid.
Also, when going back and studying, it's not the best idea to do your homework immediately and then do it one big go and not worry about it anymore.
I suggest that you take an hour to two hours break after getting home. Eat a snack, go outside and take a walk- perhaps think about what happened that day in school- and then, when you come back in, get down to your homework.
For science, it really is best to read the chapter all in one go, and then to go back and pick out key words, sentences, and other things that you think your teacher might make a point of. It's not a good idea to take notes on the chapter that are just regurgitating the entire chapter back out.
For math, it's good to do about ten to twenty problems and then see if you got them right. Try to memorize the forumals and such during this time.
After about 30 to 45 minutes, take a 15 minute break. It's been documented that your brain is only really active on one thing for about 30-45 minutes- and then it needs to rest. During this time, it would be a good idea to go and do something else for 15 minutes (take another walk. You can never get enough exercise). Hell, fold laundry. Whatever gets your mind completely off work for that 15 minutes. Check your e-mails.
But after that 15 minutes, go back to working on the homework. You'll find that your mind is refreshed, and you will work quicker.
Also, it's been shown that the brain is actively working during the hours that we sleep. While we dream, the brain will go through our memory and basically delete whatever it finds inconsequential and unimportant. That's why we can't remember everything about the day before- if it wasn't a big enough to-do to remember, the brain will wipe it out of the memory. That's why it's key to do your homework. The brain will pick up the reminder that doing the repetitive homework gives out, and will store the information in your long term memory, instead of keeping it in the short term memory.
If you do it again the next night, while briefly, for 15 to 20 minutes, go over what you did the night before, the brain will keep this information fresh in your mind. It's part of the reason why teachers give homework and not just because they hate our guts.