Class Size: Research can tell you just about anything you want it to.
I was able to keep my class size at 20 to 23 students. There were times
that the class became too small (11 to 13) to allow good interaction
between students. Although really small classes allow you to attempt
things you would never attempt with a larger group. Some of the benefits
of reasonable class sizes are: the comfort level or the teacher and the
student as well as greater personal contact and individual attention.
I doubt researchers take into account different types of subject
content or how teaching styles could differ in smaller classes.
A ceramic class works better with smaller numbers, while a band class or
vocal music teacher wants a much larger size group. I suspect the
studies were done on a math or language class. Another problem is
than few teachers adapt their approach when given smaller numbers
on the rare occasion it happens.