In the United States, all powers which are not assigned to the federal state by the U.S. Constitution are reserved to the individual states. Since the federal Constitution does not mention education, and the U.S. Supreme Court has held conclusively there is no federal Constitutional right to an education, public education has always been under the general control of the individual states. The steadily expanding role of the federal government in public education since the late nineteenth century has recently become a subject of heated debate, as many states (and more than a few Senators and Members of Congress) perceive the U.S. Government to be overstepping its constitutional bounds.
The systemic breadth required to implement statewide public education is such that most states employ a three-tiered model of decentralization that parallels the general decentralization model of state/county/township. To wit, there is usually a state superintendent of schools, who shuttles back and forth between the state department of education, the state board of education, and the state government itself. Statewide education policies are then regionally decentralized to intermediate school districts, or their equivalents by other names. These are invariably associated with counties, or with groups of counties; but the boundaries are not necessarily the same as the county boundaries. The intermediate school district is constituted of however many local school districts are assigned to its jurisdiction.
For example, the Washtenaw Intermediate School District is one of Michigan's 57 regional intermediate school districts, created in 1962 as part of a reform to Michigan's public school system. (The state has 83 counties.) It is constituted of the Ann Arbor, Chelsea, Dexter, Lincoln, Manchester, Milan, Saline, Whitmore Lake, Willow Run, and Ypsilanti public school districts. Although centered on Washtenaw County, hence the name, it does not include all of Washtenaw County in its boundaries. Small to noticeable parts of Washtenaw County are served by local school districts that are part of the intermediate school districts based on the neighboring or nearby counties of Wayne, Oakland, Livingston, Ingham, Jackson, and Lenawee. Likewise, local school districts based in Washtenaw County include parts of neighboring Lenawee, Jackson, Livingston, Wayne, and Monroe counties. Fully two-thirds of the Milan Area Schools district is actually located in Monroe County, but at the time the district was established, all of its schools were in Washtenaw County.
In most states, these county and regional "intermediate" school districts and controlling boards merely implement state education policy at the local level, and provide a channel through which the local districts communicate upward to the state board of education, state superintendent, and department of education.
Local school districts are managed by local school boards, which own and operate the public primary and secondary schools within their boundaries. They typically have no authority over private or parochial (religiously-affiliated) schools, or over home-schooling. Michigan and Iowa, however, limit home schooling to the parents of the children, and require the parents to be certified teachers. In California, where - as in most states - the licensing of teachers is limited to the public schools, teachers are not "certified"; they are "credentialed."