My mom keeps making me skip school to help her

I mentioned in my last post that I was already supposed to be able to start school on the 2nd and i am planning to go tomorrow because I at least need to see my classes before I'm all set on being there, I don't even have enough clothes like certain shirts and stuff yet. And I don't even know what I'm going to wear. 

But my mom needs me to stay again because she needs help with getting everything out the storage. We spent and average two days putting everything IN because we have a limit with the truck. And we need to return it as soon as possible. But the thing is there is no one else able to help her it's always they are too busy or they just don't come. 

I'm the only one in the house that can help her, I'm the oldest so she has to arrange plans and for me to help her with them but it's getting to a point where I seriously cannot keep doing this with her, I hate Missing school when I have to be some place with her I'm the only one in the house that has to help because nobody will. 

8th grade up to now as a junior she has been doing this, I already have days where I don't come because I just need a break but she's making it harder too. Those two or three weeks I had to skip school in 8th grade because my sister had them off and I needed to watch her while my mom was at work was the closest to me almost failing my classes (well I didn't care for it as much because I knew grades in middle school didn't matter to colleges) but either way I can't keep trying to find excuses for her to my teachers because they will get suspicious. They keep complaining about me not coming to school and I don't wanna come back to them considering bringing me to court or CPS.

I want to go to school I really do. But it's like I have no choice with her.