DS6 goes to a charter STEM school that limits its calls size to 20. This stays the same all the way up through 8th grade. The public K classes that I observed the year before DS6 started school were around 28 per class if I recall correctly. They tried to "differentiate" in those classrooms but like ColinsMum said- it really ended up being a "high" "medium" and "low" version of the same lesson. None of them was even remotely aimed at DS's level (and that was a year BEFORE he started K). His teacher this year was able to do things on a much more individual level than we would have seen in the huge public school classes. We're VERY happy with our school.