Yes, I agree with the advice above. But meanwhile do your best at school, college is the direction you should take. Junior college is usually a good option for witnesses unless there's a way you can go straight to university. Also, if you have a job, sock away as much money as possible so you can use it towards college. Don't give in to the the temptation to buy lots of clothing or entertainment. In your particular situation it is especially important to have cash for when you choose to move on from this religion.
Talk to the councillor at school about your situation. She will do what she can for you, and possibly even get you scholarships.
You are DEFINITELY not alone! Even tho I stayed with the witnesses for way too long, I felt like you did when I was in high school. Unfortunately I believed part of it, so got baptized etc etc. You have a fantastic life ahead of you! Stay positive and be an advocate for yourself.
edit: yes, as one eyed joe said, tell us more about yourself and your family situation, we can give you more specific advice. Love!