I don't want to stay in an expensive private school
Why do you not want to stay in the school?
I'm more likely to be miserable there
Many people would love to be in that position your in. You should be more grateful that your family was able to help you with your education. Remember that this will help you a lot in the long run.
I feel the school thinks of me as a waste of space and money.
Remember that these schools are very selective in who they accept, so if they didn't want you there, they wouldn't have let you in in the first place.  If your teachers seem to be too hard on you, it is because they are pushing you to succeed.  I think you should try your best with your studies, and you can use this experience to get into a good college and a good job.