please someone help!

I think the best thing you can do is try telling your parents to lower their voices down a notch. If that doesn't help than try going to someone's house for a while to do it- like on of your friend's.

If it's the kind of stress that turns into anger then try screaming into a pillow and just laying there for a bit. If its not that kind of stress then try finding something that you like the smell of like a scented candle. And if it's not too hot then you can wrap yourself in a fluffy blanket.

just do something that is calming, like sleeping or reading.

or if youre brave enough go downstairs and tell your parents that their fighting is stressing you out, and see if that solves the problem

Try writing about it. It usually helps me.
It works better if you make it out to be a letter to someone who is stressing you out the most (In this case, it's your parents and teachers) describing how you're currently feeling.
Don't worry, you don't really have to give it to them though... It's just an amazing way of venting for me.

I feel your pain, it happens. Honestly, I would move outside or to another room just to focus. There isn't much that you can do with fighting parents, but homework can be done in no time.