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While attending high school, the best study skills i found were to break things down into smaller portions, critically look at what the assignment was calling for, and then go about solving the issues in a quiet place, no tv, no radio, mp3, cell phones, or distractions from other family members.
What is your life outside of school? Are you also working part time. That can have a big affect on you being able to study. Also there are endless resources online that can help you with the subject in a condensed form. For example, if you don't understand an equation in your Physics class look it up on YouTube where someone can explain it to you and you can also re watch as many times as you need to understand.
Some skills that you benefit you throughout High School and carry over to your college or work are: time-management, note-taking, organizational skills, and not procrastinating (to prevent any stress). I would suggest you to use an agenda to help manage your time (in case you're working and going to school), as well as help yourself set deadlines. I usually tell myself that an essay/project is due 2 days before the actual due date so that I can finish it early and not have to worry about it. If i don't finish it early, then at least I have given myself some cushion-time.
Keep track of what assignments are due when and get them in on time.
Anytime your teacher says "This will be on the test", write it down and remember it.
Review recent material at least once every couple of days, and review as much of the material as you can once a week.
More than anything, try to identify what you're meant to learn from the curriculum rather than spitting factoids back out. The factoids will get you a passing grade, maybe even an excellent grade, but you won't remember half of them six months from now. The more you really understand what they're trying to teach you and why, the better you'll be able to identify the subjects you are interested in, maybe even passionate about, and that whole "what do you want to major in"/"what do you want to do with your life" question will be a lot easier to cope with. And you'll enjoy school more.