There are free online high schools available in most states in the U.S., and the majority of these schools are public. Some online high schools are affiliated with local public schools, and there are also programs that do not have a connection to a traditional brick and mortar school.
About.com lists online high schools by state, and it includes both traditional schools that are run by local school districts as well as charter schools that receive government funding. Those interested in free online high schools can search using a variety of factors depending on the website.
At OnlineSchools.com, users can search not only by state but also by tuition, schedule and public/private school type.