I am guessing that this would be similar to homeschooling? I don’t know that much about homeschooling after 12th grade, but I can say that you should definitely contact your state’s department of education and ask them. If there is an option for educating yourself and earning a major, there will be steps that you’ll probably have to follow (like a once a year evaluation of your work, or a state test.) But my best suggestion for you would be to do your college work online from an accredited institution. This will be much easier, you get to work on your own pace, and you won’t be in a complete classroom setting. Try going to google and searching for online college degree, online college classes.

Some universities will allow you to earn credit by exam only…

Pick a university, pick a language major and apply….

Check CLEP and DANTES programs… to take exams for general credit exams..