How do I deal with this?

I don't like it when my sister doesn't listen to me; she takes advantage of me. Since I'm the eldest, it doesn't mean that I should be responsible at all times. I'm going to be in 8th grade in September, and after that, I'm off to high school. She leaves a mess, and when i tell her to clean it up; she just doesn't. My parents blame me for being irresponsible and unorganized, but it's not me-- it's my sister. High school is around the corner, who's going to be there when i'm not home? Honestly, would they expect me to come home and fix the problem? Geez, I have to live with hell all the time. My parents and I had a huge fight two days ago, and it's making me sick just thinking about it. I certainly think that I have no reason to apologize because they hit me for being "stubborn" (according to them) when i'm really following their rules and commands. What should I do to confront them? They NEVER listen. I absolutely blame my sister for what has happened.