My grandparents are so mean to me what should I do?

My grandma is so mean to me im15 and I'm have a hard time at school with bully's and she isn't much better she all was hollers and say she don't and when I holler back she hits me or grabs me by my hair she never care's what I have to say the bad part is I live with her and my grandpa always takes her side they don't care about me or they wouldn't do what they do I now this is a bad thing to say but I hate them