An independent school is a school which is not dependent upon national or local government for financing its operation and is instead operated by tuition charges, gifts, and perhaps the investment yield of an endowment. In England, Wales and Northern Ireland the more prestigious independent schools are known as public schools. Membership of the Headmasters' and Headmistresses' Conference is often considered as what defines a school as a public school. In Scotland, all schools not dependent on state funding are known as private schools or independent schools.