One of my DCs teachers always addresses me in writing as Ms. Kinsky.
I have the same surname as my DC, I wear a wedding ring, and often draghave DH with me, so I expect to be addressed as Mrs Kinsky, or even Mitzi (I am on first name terms with all the other staff at this school).
I find using Ms when you know someone is married a bit rude. I'm contemplating pointing out, nicely, that I'm a Mrs.