While I hesitate to toot my own horn, I should mention that I have a website for specifically this called:
Best Online High Schools
On it, I have about seventy-five online high schools with more on the way. There are so many, many choices available now that I find it difficult to keep up. It's likely worth a look.
I should mention that I am also the author of an article on this site about online high schools. It is located here:
Are you considering an online high school?
Best,
Tom Nixon