Education is headlining politics again. Class sizes or teacher quality?
From where I sit (and with the benefit of practice) the answer is….. “It depends”.
A good teacher in a large class will usually be less effective. Worse, if there are students with poor behaviour or well below norms of capability. Recall, the teacher is increasingly expected to facilitate students individualised learning: this means lots of 1:1 time. It only takes 1-2 students at Senior levels that cannot read, or write coherent sentence to consume vast amounts of a teachers time to the disadvantage of other students. Likewise with poor behaviour, 1-2 students can easily swing the entire productivity of a classroom.
Likewise, a small class with a poor quality teacher will likely be just as ineffective.
I suspect, like the author of this blog, it all comes down to money. https://libcom.org/blog/class-size-matters-money-tight-22122011