I think your post is excellent. I will post some information about teaching at secondary schools in Scotland. And how many teachers were demoralised there when the government changed the education system to a comprehensive system. In my view this was a bad change. It basically meant that the 11+ exam at the end of a pupil's primary school education was scrapped. It had been used to determine which pupils went to senior secondary schools and which pupils went to junior secondary schools. I believe in England they were called grammar schools and secondary modern schools, respectively. Pupils at senior secondary schools/grammar schools were academically inclined. Those at junior secondaries/secondary moderns were less talented and left school after 4 years of secondary education.

As a young secondary school teacher I joined the Scottish Secondary Schools Teachers Association. The other union was the Eductional Institute for Scotland. You had to join one union or the other. I felt cheated when the government of the day reduced the number of increments of the pay scale. I forget the precise details, but those teachers with honours degrees were placed on scale point 3 as new teachers. Those teachers with ordinary degrees with 5 first year subjects and 2 second year subjects were placed on scale point 1. But if you had a third year graduating subject in your ordinary degree, you were placed on scale point 2. Each new academic year you moved up the ladder by one scale point until you reached the maximum. When the number of scale points was reduced, I was unlucky in that I was caught in the middle as I had read maths for 3 years at university. When the changes came into effect, I was stuck on the same increment for 2 years!

The situation re science subjects at Edinburgh University was strange. Take physics, for example. Theoretical physics courses were physics 1A, physics 2A, physics 3 and physics 4. But arts students reading for their MA degrees could study physics 2B, and be credited with natural philosophy 3, a third year subject. I know this because I studied physics 2B in the faculty of science.

Governments have tampered with exams such as 'O' grades/'O' levels and 'H' grades/ 'A' levels to ensure that the dumbest of the dumb get some kind of leaving certificate.
Then there are league tables. It must be hard to identify lousy schools because catchment areas of a school's pupils have a major influence on a school's academic results.
The best secondary schools in Edinburgh were able to get student teachers' teaching grades from the college of education before they graduated, which was supposed to be illegal. This allowed such schools to recruit the most talented teachers! I studied for 1 year at the college of education after graduating from university.

Across the pond, university students read general studies during their fresher years. Very different from British universities. Teachers at high schools in the US are not able to move from one state to another easily as teacher qualifications vary from state to state.

I think teaching in China is generally speaking a dawdle compared to teaching school in the UK.