The French Lyçée system, which has been mutating to become more British, was similar to South Korea.

Our French teachers at the London French Lyçée were paid a lot more than the English teachers paid local unionized rates (the gossip suggested about double, but there was the allowance for working abroad in an expensive country to take into account). We also had a no strike agreement in the 1970s (for the English, not the French) with a teacher actually dismissed for going on strike when the English schools did so. The deal was that the English would be paid whatever rates the strikers eventually forced the UK government into awarding.

French staff were more likely to drive nice cars and the English rode bicycles or took public transport. The French were generally more qualified (they were called “profs” which must be telling about status), did not enforce discipline (there was a separate group of people whose job was “surveillant” or “pion” [pawn] under the authority of three surveillants généraux and the “Censeur” [I think the title was a Roman affectation, not literally the modern “censor"] acting as the assistant headmaster in charge of discipline and I think, the performance of teachers and pupils [even some of the teachers appeared to fear M. Pichon]).

My average class size was 28-32. In fact, the Terminale C, which was the élite (Mathematics specialists) had the biggest class size of all in my six-form year. There was no noticeable relationship between class size and results. But there most emphatically was between having the better Maths or French teachers through secondary school.

I was fairly lucky, I thought we had mostly good teachers in the final year of the Baccalauréat, with Maths probably the weakest (the average class score was terrible, ranging from 5% to 80% with probably a clear majority under 40%). And this is for a class of economics students not the poets in Terminale A2 or A5.

There was no noticeable relationship between class size and results. But there most emphatically was between having the better Maths or French teachers through secondary school.

I think the main purpose of Americans in lowering their class size is to be able to give enough attention to all their students per class.  In this way, teachers could easily attend to each student need. South Korea’s standard of hiring their teachers is absolutely the best strategy to improve their students’ learning.