I went to school just prior to the Boomers. We had 35+ routinely in our classes. We met in the gym and cafeteria because there weren’t enough classrooms. We had alternate day school at one point in my town, but the day went to 4:30. I graduated in 1961 and received a real secondary education. We had art, music, theater, languages, sports, college preference tracks and vocational tracks. We had real National Honor Merit Scholars and decent to high SATs/ACTs. We had time to raise the flag and say the Pledge. Our teachers had really low salaries and small pensions. Hardly anyone one had employer-provided health insurance except the government workers.
We did just fine.
it is possible with 35, but if you have teachers that can’t be fired and can’t teach 20 putting 35 in a class results ina cluster $%^&.