I really wonder how many children they can jam into a classroom. Sigh... Our school has a full-time, self-contained gifted program so at least for 4th grade on up, it will be just kids in the gifted program. Hard to know if that matters anyway.
For kindergarten, we were at a private school with only 10 kids per class, and it wasn't that impressive. It probably partly depends on the quality of the teacher and the other students too.