My wife is a teacher for an on-line high school. As a teacher, she generally likes it. She does caution, though, “I do not believe on-line school is for everyone.”
From my perspective, I see it benefiting / suffering from the typical distance learning characteristics. The socialization situation would be very different from that of a brick and mortar school (for better or worse; the cynic in me considers conventional K-12 education to be a form of day-prison for the young…).
I’m happy to answer any questions you might have. My daughter isn’t even in school yet, but I could see us considering it. It may also pair well with folks who want to home school, but don’t have the breadth/depth necessary to provide a complete K-12 education.