I moved schools senior year, although not for the same reasons you may have to, and it was fine. If I were you I’d stay in school for senior year. Some colleges require you take 4 years of science, english, etc. and most highly recommend it. If you graduate after your junior year will you be as competitive an applicant to those reach schools? (honestly I don’t know, but it’s something to consider). I would highly recommend speaking to your guidance counselor or college counselor if your school has one, reviewing the colleges you plan on applying to’s required and recommended HS courses, and speaking extensively with your family. I agree that a GED is not a good option unless absolutely necessary.