One of the concepts behind public and private schooling is to teach us how to get along with others. The good, the bad and the ugly. It's not as easy to learn that when one is home schooled, because the opportunities for interaction are almost non-existent. And, unfortunately, being able to "play well with others" is helpful in the real world - both in business and socially.
If you're really trying at your schoolwork, and still having trouble, maybe consider asking your parents about having a tutor help in the subjects that are the most challenging? The one on one attention allows you to ask questions that couldn't be asked in class. With a tutor, you can keep plugging away until you get it. Pick a quiet time to talk to your mom or dad, and just tell them, "I want to do better in school, but I need help. Could we consider a tutor?"
I don't want to sound discouraging, but it is almost impossible to get a parent to admit they were/are wrong. Yes, there are exceptions, and some very open-minded parents out there, but a lot of the time, parents (or any authority figure) think they will lose that "I'm always right" image if they concede. So don't push it. Everyone gets stubborn when pushed, and sometimes it's just better in the long run to let it ride.
So, if you want things to change, make a list for yourself. Pick out the things over which you have control, and make the changes needed. Things may not improve overnight, but you can keep reminding yourself that you're working towards something, not just giving in, and letting life roll over you.
P.S. One of the fellows I used to date had a gray streak in his hair during highschool, and it was pretty sexy.