How far is teaching Traditional Grammar acceptable in modern teaching of a language?

Does the teaching/institutionalization of "proper" grammar slow or prevent the evolution of language, and if so, does this achieve a net benefit to human communication?

• Answer:

  For the first part, it does seem to be the case that widespread education and writing slows down language change.  In part because it provides a standard, but its main effect comes from its size. Languages change faster in smaller communities. Widespread education creates a very large community.  I don't know if that "achieves a net benefit" to human communication.  There is benefit in people being able to talk to each other.  But we use language for ill as well as for good, and language barriers have never really been a major obstacle to good business. We can also ask whether the benefit to human communication is worth the cost, and there is a major cost.  Most education programs in history have promoted a standard dialect or language at the express expense of others already spoken. Often through brutal measures.  Enforcement of a socially "superior" variety has very damaging effects on people and cultures worldwide, with all the social and psychological problems that ensue from being treated as second-class because of the way your people talk.