Teachers cannot teach what they, themselves, have never learned. Our teens and young adults are part of a lost generation. They can text and tweet but cannot legibly write a paragraph punctuated correctly containing complete words which are spelled correctly.
You don't know the teenagers I know. It can be rather embarrassing when a 14yo corrects your spelling, grammar, or punctuation. It doesn't happen all that often - but enough for me to take special care if I am having an online conversation with any of them.