My best advice would be to always do the homeworks and ask if you don't understand something. It's better to ask than to just ignore it. If you ask something, the teacher will se that you are interested in the subject and therby improve your grade.
You have to be motivated to go to school, sometimes it could be hard, but you got to find it. Don't look at the school as a boring place, instead see it as a place where you can learn stuff. You don't learn stuff for school, but for life. The school is the place that gives you a good bottom to build stuff on. If you feel like everything is going down, bad grades, or so, always think positive. If you do that everything will improve. You will finally feel proud, when you see your grades, thanks to the fact that you always see stuff from a positive perspective.
Success!
