Online delivery has been quite popular at the university level. We are now seeing offering at the high school and even grade school levels.
Many offerings augment traditional face-to-face learning and/or provide professional development for teachers. Some are designed to replace traditional classrooms for select student populations.
Online courseware is especially useful in settings where content expertise is not available at all sites. One school district may not be able to offer advanced placement courses via a “real” teacher at all secondary schools because student enrollment numbers would not be high enough to support the cost of a staff member. This limitation occurs in rural areas often or in districts suffering budget losses.