"If you can do math, you can teach yourself enough physics to teach in high school."
No, you can't. Even at the high school level there is jargon, historical methodology, and domain-specific nuance that isn't accessible to the self-taught. That's true for almost any subject one might think of, in fact.
What prevents anyone from learning all they need about any subject on their own? If someone is capable of reading, it seems to me they could teach themselves any subject using books. Of course, having a good teacher to guide them in which sources to read, etc, would greatly speed up the process of learning. However, I don’t see any reason someone cannot learn any subject on their own.
Books provide the basics required to understand the field. They don't help develop intuition, methodology, collaboration, and other skills necessary to truly understand the field or teach it to others.
To be clear, I didn't write "be an exceptional physics teacher with knowledge of history, nuance, etc." - I agree that's not a trivial thing and a very desirable one. But if you need "just a physics teacher" for a given spot, I stand by my opinion.
I mean, if you’re talking about the happy path where every student understands the material on the first pass or can work out issues on their own then maybe. But that’s not how teaching or learning works for anyone, including super geniuses.
The physics knowledge isn’t the important part of being a physics teacher. The “teacher” part is. Teaching is its own discipline for a reason.
Or, the ability to explain physics to one person is not the ability to successfully teach physics to 30 teenagers in a high school setting.
Whether you could or couldn't self study to be a competent physics teacher is besides the point if you need a physics or very closely related STEM degree plus test of content competency as a condition of getting the job by the regulations if most US states. That limits the pool of applicants to people who can command better salaries elsewhere over their whole career arc for arguably a lot less stress. Thus an exceptional shortage within that specialty is more prone to happen. Lowering the standards of qualification is an option, but the author doesn't seem thrilled with that idea. So we are pretty much left with discussing a pay differential within the profession, which is a third rail topic among most teacher unions.
Do they? I read that as implying that physics teachers could potentially get some stem jobs. But is that actually true? If you can do math, you can teach yourself enough physics to teach in high school. But that gets you nowhere near the knowledge necessary for applying non-trivial physics at work.