Mine's not a teacher, but does this kind of thing. She talks over you, never listens and speaks to you like you're a child 9 times out of 10.
I have recently had my final disagreement with the woman and now DH deals with her exclusively.
It's not an easy situation and will undoubtedly lead to a build up in resentment. It's a hard situation some wives are placed in. We love our husbands, but aren't at all fond of their mothers. They made them the people they are, yet often, they have such conflicting values and behaviours it defies reason.
I don't know what to suggest.
My DH ignores his mum. I can't do that...she's not my mother. However, after a number of disagreements - she called DD Monkey legs and laughed at her hairy legs....against my better judgement, I forgave her and tried again...last Sunday dd went to a sleepover at nanny's. I'd rung to extend the playdate, to tell nanny she could keep dd for tea. MIL gleefully announced dd had had chocolate pancakes for her tea the previous night (after I'd specifically asked her not to feed dd any more crap as she'd had tons of chocolate before going to nanny's). I expressed my annoyance about this and MIL got defensive. Very defensive. In the meantime, DD realises it's me on the phone and starts fake crying and saying she wants to come home. I tried to talk her into staying, but couldn't, so told MIL I'd be over to pick her up. MIL aggressively tells me it's my fault dd is upset, I shouldn't have rung! DH had to go pick her up early as I was just about ready to kill her.
Sorry for the tirade. But MIL's don't change their spots. I try, every now and again, to be the reasonable DIL and involve MIL in our lives (I hate the fact my mum isn't nearer and really want her involved) and then I remember that she's an insane old bitch.
Try to sort out a way of dealing with her and get your DH/DP's help if you can. Good luck in dealing with this one...