It was emphasized above, for example, that in Bernstein's work, although much of it is concerned with educability, no attempt is made to examine how language is used in schools. Bernstein's model proposes external determinants of educational success: social-class stratification is said to produce different family types with different communication systems, which in turn produce different codes and different cognitive orientations in children. He simply states, without evidence or illustrations, that schools are predicated upon elaborated code, since schools are concerned with 'making explicit and elaborating through language, principles and operations' (CCC 1, p. 221) and that 'the introduction of the child to the universalistic meanings of public forms of thought. . . is education' (CCC 7, p. 225, emphasis in original). It will become clear below, in studying actual fragments of transcribed classroom lessons, that classroom language is often highly constrained in some obvious ways, rather than 'elaborated'.