What's funny is if the grammar used in this letter had been the same as a post on FR by a freeper, the grammar police on FR that defend this teacher would likely be the ones shredding a freeper for their comments. Irony.
I have posted on internet boards for years and have never criticized anyone's grammar. I've never personally observed "grammar police" at work on these boards, though I've seen "spelling police", whom I find especially petty.
I'd rather exchange messages with someone who is forthright, honest and has something to say, albeit a poor speller, than with someone who is adroit at spelling and grammar but not a critical thinker. Just my humble opinion. (oops! that's not a complete sentence!)