If you are 15, you are minor; as a minor, your parent(s) have the right to decide where and with whom you live. When you turn 16, it *may* be possible to have a court declare you "emancipated," which would let you decide where to live, but you'd need to show the court not just that you are mentally competent but also 1) good reasons for wanting to be emancipated; and 2) that it is realistic or feasible for you to manage your own affairs. To try to be emancipated, you'd need to bring a legal action in court.