The idea that class size is a key leading to higher student success rate is a misnomer. Studies over the past 15 years have consistently indicated that class size has little (sometimes even converse) relation to student success rate.

http://www.npr.org/2011/03/29/134956184/school-founder-says-... , http://www.pioneerinstitute.org/pdf/010326_stergios.pdf

A lot of the top performing countries in education have extrodinarily high average class sizes. Taiwan has 44, South Korea has 49. http://www.arthurhu.com/index/classize.htm .

Although you aren't entirely off base, in Taiwan many math and science based classes can be 150 students or more, which I'm sure pulls the median.