Education in Spain is regulated by the Ley Orgánica de Educación (LOE, Organic Law of Education) that expands upon Article 27 of the Spanish Constitution of 1978. Education is compulsory and free for all children aged between 6 and 16 years, and is supported by the national government together with the governments of each of the country's 17 autonomous communities. Once students have finished their Bachillerato, they can take their University Entrance Exam (Pruebas de Acceso a la Universidad, popularly called Selectividad) which differs greatly from region to region. The compulsory stage of secondary education is normally referred to by its initials: ESO (Educación Secundaria Obligatoria).