ames, you wrote, “The rabbi’s point was, that no matter how good a female teacher is, she can’t possibly have the breadth and depth of knowledge in areas such as halacha and deep hashkafa.”
That really depends on the teacher. Many of the male teachers I’ve had for limudei kodesh subjects seemed to feel that they did not need to prepare a lesson, but that their “breadth & depth” of knowledge would suffice. These teachers were incorrect (except for the posek I mentioned previously); their lack of preparation hurt their ability to teach & probably contributed to their failure to control the class. I think if these male teachers had been teaching boys or young men, they would not have had this attitude.
The female teachers I’ve had usually prepared the lesson, so even if they had less “breadth & depth” of knowledge they were able to teach effectively.