I live with my mother and step father and two little brothers and we are living at my stepfathers parents house and I want to move out because I hate the school and I do bad there but I want to move in with my grandpa and I'll have a place to stay,a car and will be provided for and my grandpa says this is OK and I'd willing to do all that stuff for me but my mom won't let me and if I don't move with him ill just end up dropping out of school where I'm currently at and the school I was going before I was able to keep a 3.5 Gpa and was in sports I NEED HELP what should/Can I do?

You have no rights until you are 18, sorry. That's the law. To be mature about it, find a calm moment when you can get your mother and grandfather talking to each other. Make a list of the reasons it's a good idea to live with him. Make sure you mean it if you say you will help him around the house, and won't expect him to shop, cook, do dishes, laundry, housework, and other chores and errands. Most teens have no clue about all that stuff, and your mother may know that you don't lift a finger, and knows that what you want is an unrealistic burden on your grandpa.
Just the basic question of doing errands when you are 16 and a high risk driver is huge - you do realize that grandpa's car insurance will skyrocket if he lets you drive, right?
This is just the beginning of what you have to consider.

If grandpa is willing to help you, have him file a petition in court so he can have custody over you. Before you do anything though, take a step back, because you sound a little desperate here. What is it that's so bad about living where you live now, other than "school sucks"? Why can't you be in sports at current school?
You said that if you move in with grandpa, you will have a car and he will be providing for you, and you will have a place to stay. Newsflash: you already have a place to stay, you can work to provide for yourself instead of living off you grandpa, and you do not need a car at this age.
Do you do everything that your parents tell you to do, or you don't and that's why you think they are no longer cool and you want to move out?

Sit back and think about everything before you get out there in the big world, as a high school drop out- if you think life suck now, try finding a job with no education!!

Grandpa won't live forever to provide for you!!