Now, if they let teachers pick their students (ha, that would be private schools), or be guaranteed a learning-ability spectrum within normal range (nope, called "tracking" , or actually give them books and materials and assistance (sorry, no money...pull out your own credit card), then perhaps. We lived through the 32 per classroom years and am thankful for lower class sizes in the elementary schools that came later, at least in California.
A "good teacher" can get a seriously "bad class" and it's not that hard because we could not (at least then) retain/fail children who lag behind for intellectual, family, language, disability or cultural reasons. They just get passed on up. I recommended two 1st graders for retention because after being almost privately tutored by the half-time aide I had (who got cut the next year), they still could not understand the most basic tools ... shape recognition and number concept...crucial to reading and arithmetic.
Also recommended a 3rd student who was clearly intelligent, but spoke no English, came in late in the year and needed to get 1st grade concepts to move on. Even his parents and the ESL teacher agreed. He probably would have made it anyway, but it would have been better for his future educational development. Can you imagine the "test results" of these kids that year and the next?
Refused on all 3.
Also, I had 2-3 students who were reading at 3-4th grade level, parents involved, motivated, etc. I am sad to say that they pretty much taught themselves...and did very well on the tests. This was just one year. After 5 years, I got tired and decided to work for a living wage.
Sorry for the rant. Maybe it's different today. As they say, It's Complicated.