On-screen (or on-panel?) all we see of Kawawa's teaching is her basically telling her students to git gud.
Maybe her off-screen teaching was better, but it's equally likely that Asuza's bet motivated them to study harder (or Kasumi's fear of her mom, in her case).
Uh, on the same page you link, we see her explaining to Kasumi in details about sin and cos. The whole "git gud" as you say, is in response to Asuza asking about how she, herself, study for exams. It's pretty much shown that when it comes to teaching, she does a proper job, even if it mostly happens off pannel.
I think calling her a crap teacher just because the author didn't bother showing the whole lesson and chose to give focus on the penalty game and Kasumi taking barely readable notes is exagerated, especially since we could see it gave great result in the end. :/
