In days past, most of the online programs at the college level were at second (or third or fourth) tier schools with the Harvards and the Yales not particularly interested. This has begun to change and, to me, this could be a real boon for serious high school students who want to learn at an elite level.
Either to supplement what you are doing in your public school or in your homeschooling, you should consider taking advantage of what is offered by MIT for free. This may be where some of the elites draw the line; not giving course credit. Yes, they might provide some resources for learning, but may not give you credit for doing so.
MIT has an initiative called OpenCourseWare that provides instruction for many of their courses. This includes lecture notes, readings, tests, and sometimes video lectures. However, no one is grading any of it, so you need to trust yourself not to cheat.
I think that this could work equally well for serious-minded college and high school students. To read more about it, see: