Fast...
The teenage years are going to be the most stressful for a parent and their child. I know, I have a 15 year old son.
I have also struggled with my son's poor academic performance. It can be extremely frustrating for a parent because parents know how much is riding on good academic performace. Doing well in high school also establishes good habits that will carry through for the rest of your life.
I know my frustration with my own son is magnified because he is smart and capable yet under achieves. I have probably erred on the side of letting him fall on his own face. There is no right or wrong answer to these problems.
But, if your mother is grounding you for not performing well in school it is because she cares about you and loves you. Frankly, I think it would be far worse if you had a parent that didn't care about how you did in school.
I really don't think that the answer is leaving home. If you do that you are only going to increase the tension with your mother. Many, many times teens that have a terrible relationship with their parents in their teen years wind up having wonderful relationships with their parents when they get a little older. Don't throw that away.
I would suggest that you find a time when your mother is not upset with you or anything else and sit down and talk with her. Really talk with her. Tell her how you feel. If you are doing your best in school tell her that. Explain to her your plan for improving your school grades. You must have a plan to do this..... very important. You need to show your mom that you are being proactive and responsible, she will respect that.
I am not saying you are doing this, but many, many times teens like to cast blame on everyone but themsleves, especially their parents. If you can show your mom that you are willing to accept responsibility for what has happened to you in school that wil be huge.
It would also be a good idea to tell your mom that you appreciate that she cares how you do in school. And, there must be other things that your mom does for you that you could tell her that you appreciate those things. You would be surprised how many parents feel under appreciated by their teens.
Just try and be open and honest with your mom. You are at a point where you are on the verge of being a young adult. As an adult sometimes you have to suck it up and take the first step in solving problems in any relationship. your mom will appreciate that too.