Availability: Functioning educational institutions and programmes have to be available in sufficient quantity. The availability of trained teachers and teaching materials, issues of buildings, sanitation facilities for both sexes, safe drinking water are among the most crucial elements under this criterion. The Framework Convention includes different levels of obligations for States with regard to availability in the different levels of education. Accessibility has three overlapping dimensions: non-discrimination, physical accessibility (appropriate geographic location, transportation, modern technology) and economic accessibility. Primary education must be ‘free to all’ under human rights instruments.53 In Europe, Article 17 (2) of the Revised European Social Charter requires State Parties to provide children and young persons with ‘a free primary and secondary education’. Acceptability: the form and substance of education, including curricula and teaching methods, have to be acceptable (e.g. relevant, culturally appropriate and of good quality) to students and parents. Acceptability is thus relevant for the whole physical and social environment of education. While this criterion is of particular importance for national minorities, it does not exempt them automatically from the objectives and standards defined in the educational system of the State. Adaptability: education has to be flexible so as to adapt to the needs of changing societies and communities and to respond to the needs of students within their diverse social and cultural settings. This must be kept in mind as both minorities and majorities are developing entities as are persons belonging to them. Minority and majority identities need to be constantly discussed and reassessed as they are not frozen. Nor are languages and religion frozen phenomena and this has also been the view of the Advisory Committee in its work. 53 General Comment 11 (1999) on Plans of Action for Primary Education of the Committee on Economic, Social and Cultural Rights elaborates on the notions of ‘compulsory’ and ‘free-of-charge’ education. 28