Basil Bernstein's work on Language has run the whole gamut from being considered breakthrough and profound material to a brief early period of having the deepest suspicions cast on its conclusions.
He developed a theory over 40-odd years, that language is split into "codes", and that we all use differing "codes" depending on where we are and who we are talking to. He describes one code which a child would use at home, another with their friends, another at school and so on. One child could have many different "codes" or languages. The impoverishment would come when a child had very narrow influences imposing a "restricted code", so that in some circumstances s/he could not perform as well as other children, or have any parity.
Suspicions were aroused that the implication of this was that the language used by working class people, or those who communicate in different cultural varieties of English, was in some way deficient. The truth of the matter was quite the reverse. He explained that "Code" is not synonymous with "dialect". A "restricted code" is one which presupposes a certain amount of shared knowledge between the people using it. An "elaborated code" would be understandable by a stranger. The ideal would be for a person to be able to talk in many "codes." Bernstein's socio-linguistic discoveries showed time and time again that the more codes a child had - the more "languages" they spoke - the faster their learning progressed.
Bernstein was committed to achieving an Education system which would afford equal opportunity to all. Although this particular work was written in 1971, it forms the basis of studies into language and communication even now.