They often have TAs who cover office hours or the discussion groups. My daughter was a TA for Wyoming History, a required course for EVERY student at Wyoming so the lecture classes were 100-150 students. The students had 2 large lectures and 1 discussion group each week, and could get help from any prof or TA during office hours
Other daughter went to a school where I don’t think there was a classroom that held more than 60. The school did have an auditorium (much like an old high school auditorium) that held about 250. Most of the students didn’t care how many other students were in their math class and wished some of the sections (at better times) had been bigger, or that the labs were bigger so they could go to another section, but they were what they were. She never had an issue getting time at office hours even if that prof taught 3 sections of Calc I with 150 total students. Other daughter might have had more trouble getting to a professor who taught 3 history classes with only 24 in each section (the max for upper division at her school) because that 1 professor may have had only 1 or 2 hours of office time per week, and the 3 courses weren’t the same so had different students with different questions looking for help, and no TAs.
Around here, school districts limit class size to 25 in high schools. Except for AP! Those are unlimited, so an AP Lit class can have 40 or 45 students while English 10 can only have 25.