We talked about this at our school and nixed it because several of our teachers, two of whom are single parents, have students in the school. They can't be in their classrooms, teaching, and at home with their students, supervising.
We're going to be doing this in DD's middle school, but we're a tiny school so everyone is on mostly the same track. There is only one track for 5th & 6th grades and all of the kids in those grades move as a unit, so moving the teachers around works. It works, though differently, for 7th & 8th as well because the variation is in the math track - the "standard" track is on site, the "advanced" track is dual-enrollment at the high school next door - and in foreign language, which is entirely taught at the neighboring high school but the whole grade still takes those classes in the same hour. The difference is just which go next door and to which classroom, and which stay in our building. But in bigger middle schools and in high schools regardless of size, the kids don't move as a group from class to class - a student can be in the standard level of English but advanced math, or standard math but AP history, etc. So they have to be able to rearrange themselves between classes.
And for many, it isn't even a question of money. In a lot of rural America, high speed internet simply isn't available. Unless something radical changes in our political climate, we're not going to suddenly and in a time of budget crisis make the kind of investments in broadband infrastructure that were made during the Depression to extend electricity to rural communities, but that's what would be needed for us to really think about online schooling as a way of reinventing education on anything more than a short-term, emergency solution.