Many states consider certain online schools the same as public schools. A charter-type school employs teachers to teach online, grade online, and schedule activities for the students throughout the school year. These type of schools cover the cost of books and admission requirements. As long as you enroll when there is availability, you are guaranteed a spot. Reputable companies include K12 and Connections Academy; availability varies by state.
Numerous home-school curricula offer courses in an online setting. These schools receive tuition just like any other public school. Requirements vary from school to school, but they do provide transcripts at the end of a school year to those interested in enrolling in higher education.
Many of today's home-school curriculum include an option to do your learning online. These operations check most of your work almost immediately as you turn it in while still allowing you to move at your own pace. In most of these cases, you pay for the curriculum and then continue to home-school using it throughout the school year.