LANGUAGE CORRECTNESS AS AN APPLIED LINGUISTICS PROBLEM
Social class markers
When parents say of their teenage children that they don’t understand their language, what they probably mean is that young people use somewhat different vocabulary; also perhaps that the topics they talk about are not those current among their parents’ generation. This difference is an example of the general case that different groups mark their speech in ways that distinguish it from that of others, sometimes in grammar, more often in vocabulary and most of all in pronunciation. At the same time these different groups share the same common language, which allows them to communicate readily with one another, but in subtly different ways, recognized by everyone, salient socially not linguistically.
One of these group distinctions is that of the linguistic markers of social class, which in English has been satirized as marking the U(pper)–non-U(pper) dis tinction. Examples from Ross (1978) include:

Does it makes any sense to regard the U usages as more correct than the non-U? This is indeed what Ross suggests. He uses the terms ‘upper class (abbreviated U), correct, proper, legitimate, appropriate … to designate usages of the upper class; their antonyms (non-U, not proper, not legitimate etc.) to designate usages which are not upper class’ (ibid: 91).
Surely these examples are so unimportant that the argument must be fatuous. But that of course is Ross’s point, that these variants are linguistically trivial and therefore do not hinder communication across the class divide but at the same time mark the social distinction very clearly. Ross calls them ‘philologically trivial and, apparently, almost all of a very ephemeral nature’ (ibid: 104). Socially, however, they are not at all trivial because, if Ross’s argument is to be accepted, the non-U speaker can never convincingly become a U speaker. The non-U speaker may learn to use U usages but always too late since new ones emerge to maintain the social difference.
This is not, however, the case with the use of non-discriminatory language, since the campaigns in its favor take for granted that it is possible to become nondiscriminatory language users. In so doing, we are also choosing what may be regarded as more ‘correct’.