Depending on your age you should probably see a Social Worker. They can guide you through the legal, emotional, academic, and financial processes. Try googling "Department of Social Services in _________________________" and then put in whatever city and state you are in. Lawyeres are to expensive, definitely go with a social worker. Or even counselors at your school could provide advice.
And yes, your parents have to financially support you until you're 18 unless they offically give up parental rights in a courtroom or you get emancipated (like a divorce from your parents in which you have to prove that you can support yourself without them) or some other family member agrees to take you on as a financial responsibility.
And if youre under 16 and stop showing up to school because they kicked you out, they could be arrested. Unless they report you as a run away, then you could be arrested.