The online school that interests me most is the EPGY Online High School . An article describing one young woman's experience with it is

http://www.pinnaclenews.com/news/contentview.asp?c=267285
Ready for the Ivy League
Friday, March 19, 2010
By Katie Moeller

Of course many students take EPGY courses before they are of high school age. AOPS offers math courses and a programing course but is not a full-fledged high school.

Maybe it is best to mix and match online courses from various providers, based on their relative strengths, but this will complicate the creation of a high school transcript.

"To see what is in front of one's nose needs a constant struggle." - George Orwell