Advancement (UK)

I've taught ESL in China. Chinese classrooms from elementary school, middle school, high school, and college are huge. There can be anywhere from 40, 50, 60, or 70 students. One teacher I met had to teach a high school class of over 100 students. Now I am sure everyone knows the answer to this next question of "how can one learn a foreign language in such a class?" The answer is not extremely well. As a result, while the student has learned English for five, six, or seven years, only a small minority can communicate at a somewhat effective level.