That's one of the supposed benefits of flipping the classroom, so rather than deliver a 'lecture' to the pupils during the day, and they do exercises via homework at night, they watch the lecture online at home, then go through exercises during class, where the teacher can then provide individual support.
If you reward a teacher with progression, aren't you then taking that teacher out of the classroom? I don't know that many head teachers actually teach much, as they're in what is essentially a management position (which they may well not be trained for either).
Yes, you are, but you improve the underlying system so that everything improves organically over time. So the cream rises to the top, but the personnel under them are better developed too. Everything goes up a notch.
What you've got to remember is that these very same teachers went through the same system to become teachers, so they inherently have the weaknesses the system promotes. For example, most teachers are weak at maths in Britain because the maths system in Britain they went through is weak.
So that's why it needs to organically change. Just offering teachers money to do their jobs better isn't going to work, because most don't have the ability to raise their game - despite the delusion that teachers are feckless and lazy, the vast majority work their arses off. They're the proverbial "dogs of war" who keep trying but don't have the tools to do the job.
So it's a generational improvement that is needed. The system needs to be adapted, not for instant results, but long term, so the next generation of teachers are starting on the right foot.
This starts from early intervention in childhood, detailed in the Allen Report, to encourage good learning and emotional practice from an early age, strong attachments, good frameworks, less red tape for teachers, an aim to teach the subject rather than tickbox the syllabus, performance development based on career progression, identifying strengths and weaknesses etc.
That's why I'm disagreeing with FLHD - yes, you can identify that teachers aren't at their most efficient, and it's easy to slate them for it, but you have to look at the tools they are given and the overall system that has allowed them to exist rather than just wave a bit of money at them in the hope they respond to it.