I always fully agree with these threads when they come up. I am an unashamed and incorrigible pedant. 
"Should of" and "would of" are pet hates of mine. They irk me, although I don't usually say anything about it.
I do think that standards of teaching (of English) may have declined in recent years. A couple of years ago my youngest daughter wrote a piece about the Queen's diamond jubilee. Instead of writing corOnation, she wrote corAnation. It was repeated many times throughout the piece of work and the class teacher had not picked up on it at all.
I have seen displays on the walls in schools with glaring errors in the work. In one piece a girl was discussing her horse. Lovely, or it would have been if she had not referred to the horse as a hoarse. It had clearly bypassed the teacher too.
As for text speak, I had better not even start.