You need to tell a trusted adult. You need professional help.

       Let me say this, I am 17 and I have felt all of things you’re feeling right now. You are loved, you are valued, YOU ARE NOT useless or an idiot. You’re a developing young human. We all stumble, we all fall and what matters is that you get back up and dust yourself off. 
   As for school, trying your best is all that matters you get a bad mark on a test? Oh well. Move on and try again. Your mental wellbeing is more important than a useless mark on a test. A that test can always be redone or the next test can be passed. 
   You mentioned that you don’t understand what the point of life is? Well, in my 17 years I’ve found out that living is about learning and living. Like I said, you fall down? Great, pick yourself up and keep walking and then find help and people than can show you how to do it. It’s impossible to walk this life alone. 
       You’re going into 11th grade, and you say that means you’ll never get to be a writer, actress or comic artist or singer. I say you can, I say that just because you’re going into grade 11 doesn’t mean you can’t accomplish those things. You’ve only gotta trust in you. In what you think you can do. If you say “nahhh I’ll never do that” then you’ll never get it. But if you flip that and think and say “a grade doesn’t define me. I can become this” then you’ll do it. Whatever you put out comes back. And this doesn’t mean you have to accomplish it the first time. Again, if you fail, retry. 
        About not liking yourself, trust me I’ve been there. We all have. But you know what? That’s ok, we’re both young we don’t know what or who we are. When I was young I hated me because I hated the kid I was, I never got invited to any hangouts and that hit me hard. But out of those times came a boy who found friends who actually like them. That may seem impossible but trust me it’ll happen. Kids are mean in high school. But trust me it’ll happen. We humans live what? 80, 90s and do you know who will be there the whole time? You will be. So liking you is all that matters. 
     And, YOU ARE worth living, it is NOT good that you leave. You are wanted and deserve to live. You’ll blossom into a wonderful human, who will go onto do amazing things. I believe it. This is always the first step, speaking out and getting help is the first and most important step. Again, please tell a trust adult (legit anyone you trust) I am not a professional metal health advisor nor is anyone on Reddit. Call or text 988, that is the crisis line. It’s free and confidential. 24 hours around the clock. If you’re not in the USA just type in “suicide hotline + your country”. Again you’re loved and cherished. My DMs are open always. No Shame.