<p>I think there are fewer well-qualified physics teachers than, say, biology. So much so that there is actually a specialty at the University level of the teaching of physics. eg. <a href=“http://depts.washington.edu/uwpeg/”>http://depts.washington.edu/uwpeg/</a> If you look at the people in this program, you will notice that these are largely physicists. They are not “education school”.
I’ve not heard of a comparable specialty in biology or chemistry. </p>