Flipped Classrooms and Class Size

The flipped classroom (Amazon link to cited book) doesn't depend on the Khan Academy. I note a New York Times op-ed on Turning Education Upside Down

Three years ago, Clintondale High School, just north of Detroit, became a “flipped school” — one where students watch teachers’ lectures at home and do what we’d otherwise call “homework” in class. Teachers record video lessons, which students watch on their smartphones, home computers or at lunch in the school’s tech lab. In class, they do projects, exercises or lab experiments in small groups while the teacher circulates....
Like everything disruptive, online education is highly controversial. But the flipped classroom is a strategy that nearly everyone agrees on. ... many people are holding it up as a potential model of how to use technology to humanize the classroom.

It is a strategy to maximize human contact by teachers. Interestingly, once we learn to use it effectively, there is really no such thing as "class size". Teachers spend their time interacting with small groups and individuals, no matter whether there are 20 students per grade or 2000.