Teachers like this exist. One of my kids had an elementary school teacher like this. Two examples:

1. The math assignment was about currency denominations; what coins and bills you need to make up $7.42, for example. My kid answered using $2 bills (uncommon in the US but still printed), as we have them at home. Teacher marked the answer wrong because teacher didn’t mention $2 bills in class.
2. The writing assignment was to rewrite the Snow White story from the perspective of another character. My kid, having read a bunch of those “twisted tales” and recently fallen in love with “Wicked”, wrote from the evil queen’s perspective and made her a sympathetic character. Teacher marked her down for “changing the story” without acknowledging my kid’s creativity. Teacher did not back down when we confronted her on this during our parent teacher conference.

(FWIW, in both cases we reassured our kid that they did great in both cases, and that we were proud of them.)

Boil ‘em, mash’ em, stick 'em in a stew