Reflect upon the fact that college instructors do not need an education degree, they just need to know the subject.
For the shortage of high school STEM teachers, I would just change the rule to: if you have taught the subject at college for two years, then you are automatically qualified to teach high school classes.
Do you think there are 3.2 million such people who would be willing to do the work?
I was a ground, simulator, and in-flight instructor in the military. I taught college as an adjunct. My old school district approached me about coming back and teaching STEM.
I’d only need 2 years of “education” courses, and take an immediate 70% pay cut.
I passed on the “opportunity”. . .