There is a very simple system...
for solving such problems. You have to separate physics education into three levels:
-physics scientists: they only teach at universities, but usually do the research work
-physics engineers: they work in the industry (this is the best paying one)
-physics teachers with a university degree: they can teach at a university or in high schools
-physics teachers with a college degree: they can teach in elementary or high schools
-general teachers with a college degree: they can only teach in elementary school
This way, the teachers who chose the easier, shorter and cheaper /maybe free/ college degrees have to teach in schools, because they don't have the qualification to work as scientists or engineers.
Making every teacher take at least 2 (an average of 3) specialisations to get a degree usually results in teachers who can teach maths, physics and chemistry/biology. Any combination is possible, but I've never seen a teacher with physics and literature combined, but it's possible. (the usual other combination in the east european country called Hungary is to learn literature, history and grammar together, with art and foreign language teachers in another group)
I just don't understand what's happening in England, but I fear that the rest of Europe will soon starts to copy it.