I once read a joke that goes like this: A school teacher went to visit a student's parents to talk to them. A 6-year-old boy answered the door. "Are your parents in?" asked the teacher. "They was in, but they is out now," the boy said. The teacher was shocked. "Was in? Is out? Where is your grammar?" The boy said, "In the kitchen making cookies."
I read an online article a few years ago, about a man who had caught his 18-year-old girlfriend with her 48-year-old math teacher; there was a fight and the teacher was stabbed to death. It took several readings before I could ascertain this, because the article was written in a very confusing manner. The way the first paragraph was written, it appeared that the 18-year-old girl had been stabbed. However the second paragraph said that the boyfriend had killed the teacher. Further down, the article stated that the girl had been both a math student and a math teacher at two different schools. How is such a thing possible?
What was clear to me was that whoever wrote that article should have been sent to grammar school. Or at the very least, read the book Eats, Shoots and Leaves by Lynne Truss, which is a rant against poor grammar and diction. Unfortunately schools are not doing their job of teaching the fundamentals, and the number of failures and dropouts is increasing. How can we be expected to understand each other and the world if people can't communicate properly?
The parody song "Word Crimes" by Weird Al Yankovic mocks online commenters and their poor grammatical usage. Have a listen.