OECD's PISA office[0] found that large, college-style lecture hall sized classes were optimal for teaching large numbers of students. They used this factor to explain South Korea's better educational outcomes than the United States'. South Korean high schools typically have large class sizes and evaluate performance based on regular standardized testing, whereas American schools typically try to always make class sizes smaller and use subject grading criteria.

[0] https://www.oecd.org/PISA/