I've noticed that in my neck of the woods, quite a few teachers make grammar mistakes. It irritates me. For instance, they will tell a student "you did good", instead of using the adverb 'well'. I also think that teachers are derelict in their duties if they fail to correct grammar mistakes in students. I suspect that this is a symptom of falsely placed 'tolerance' for different subcultures that is the trend today. But I think it's a mistake. Knowing correct, standard English is important. I, personally, instantly judge a person by their grammar and vocabulary. It tells me about their social background. It gives me clues as to their intelligence. Good grammar isn't a secret. Standard, well spoken English is widely heard on news programs and throughout the media. Oprah speaks proper English, as does Judge Judy and many other people who are viewed by the common person who might not be the most educated. So, I think the schools should be pushing proper grammar and I think teachers should speak it.