Pursuing alternatives to the standard educational system gives plenty of options. At the time I post this page, I feel entirely unqualified to comment any further on high school learning goals. Time will tell. In the meantime, here are some links that I have discovered during my internet forays. Also, please check out any claims of being accredited very carefully.
Students can earn a high school diploma by taking only distance education courses.
Cafi and Terry Cohen's page about homeschooling older kids through high school and college. To The Best Colleges and Universities. Her two children have diplomas from American School. For Students in California, this offers a free, distance education high school. The curricula you will find posted here may or may not meet your needs.