Well obviously you and your mom have some serious issues. There's always three sides of an argument. Your side, her side and the right side. But I've only heard your side, so I'm going to assume what's in the middle and call that about what is really going on. Not to say you're not telling the truth, but there may be some things on her side of the issue that contributes to the way she acts. Like for example, some kids see "hitting" as something completely different than really HITTING someone. I doubt that you're confusing that here, but that's just something that comes to mind. I'm just mentioning it so that you think about the little things she may say or do that get on your nerves.

Firstly, it's not uncommon for parents to be on there kids for good grades. I got all As and Bs ONCE when I was in 7th grade, and now Cs are like Fs. Personally, I block that out and give myself my personal goals, and if I meet them I'm okay with it, and if my parents aren't (I allow myself at most two Cs) then I deal with their yelling or lecture and I move on. If your mom is really on you though, and you say it's out of hand (and hitting and throwing stuff at you is way out of hand) then it may be time to speak to someone about it. Now, at first I was going to suggest your father, or in this case step father, but if he's already not doing anything about this and aware of it then there's a second option for you. Would you consider speaking to a school counselor? I know, not the favorite choice of most teens, but it's a very good option when it comes to parents and grades, and even when you put them together. If you don't want too much trouble, like with the law and stuff to get involved, you don't have to mention your mom hitting you (though I suggest you get that taken care of) and just mention that she over reacts, and if you're telling the truth about good grades and stuff, your counselor will see that and give you suggestions on how to talk to your mom.

Now, from what you said I can already see talking to your mom is not the easiest task in the world. So perhaps you can have your counselor talk to your mom for you. Like a phone call by your request informing her that the school is pleased with your grades and that you're doing well. Maybe even suggest having your teachers email monthly reports to your mom on your progress. You can talk to your teachers and explain to them the "problems you've been having with your mom and how she's been on you for grades, and you'd just appreciate it if they could give her an email every bi semester or so regarding your progress." Something like that.

As for your projects and stuff being called garbage, that can be rough. My best friend does creative stuff like that, and he takes it hard when people dis his projects. Could you talk to her about that? or maybe even your step dad? If not, show things to your friends and see what they think. I highly doubt that your stuff is garbage. Show it off and get some positive reactions to it. It won't erase what she says about your projects, but positive enforcement never hurt anyone. you can show it here too in the creativity section

As for the dictatorship. Well, when your a teenager sadly life is a dictatorship. You have no rights. Sucks huh? The best you can do with that one is go to your mom. Or maybe your school counselor might have some suggestions for how you can approach it as well. But for me, I'd just sit down and talk with my mom and explain how you've been feeling about how you have no say in things and how she treats you. Again, I can tell she's not the easiest person to talk to, but talking to her first, is a must before going to someone else. You have to exhaust your easiest options before going to someone else, or else they're going to tell you to do the same thing. It's like a protocol that you have to take. If you skip a step everyone is going to say "well did you talk to her?" "No." "Well then you didn't try. You could have done that."

If you don't want to go to a school counselor, try your step dad, another member of the family, or even just a teacher that you think would understand. If you go to a school counselor and talk about everything, they may even suggest a family counselor for you and your mom to see to get things calmed down. You might even want to suggest it. I have one, and it's changed the relationship with me and my parents to make things more fair I'd say. Adults work better adult to adult for some reason. They feel teens won't understand, they'll blow everything out of proportion and that they're wrong. So, get an adult to see where you're coming from, confirm that you're right that this is unfair, and let them speak on your behalf. Give it a try.