Private schools learned a long time ago that small is good. Why? Because parents wanted more personal attention for their children than they could get in most large public schools. They didn't want their children to be a number. They didn't want their children to be anonymous. So in small schools teachers and all the other staff members would know students by name.
The Institute for Local Self-Reliance offers more reasons in support of small schools: "One of the most effective ways to improve student achievement and curb school violence is to reduce the size of the nation's schools. Hundreds of studies have found that students who attend small schools outperform those in large schools on every academic measure, from grades to test scores. They are less likely to drop out and more likely to attend college. Small schools also build strong communities. Parents and neighbors are more likely to be actively involved in the school. The students benefit from community support and the school, in turn, fosters connections among neighbors and encourages civic participation."
This TEDx talk describes using innovative teaching methods in the K-12 classroom.
Low Student-to-teacher Ratio
Most prep schools or schools offering Grades 9 through 12 have a student population of about 300-400 students. Some schools are even smaller. As well, most PK-6 elementary schools tend to be small. Of course, you will find larger and smaller