Particular individuals who might never consider dropping out if they were in a different high school might decide to drop out if they attended a school where many boys and girls did so.
The higher the social class of other students the higher any given student's achievement.
A child's learning is a function more of the characteristics of his classmates than those of the teacher.
The educational resources provided by a child's fellow students are more important for his achievement than are the resources provided by the school board.
Grades are almost completely relative, in effect ranking students relative to others in their class. Thus extra achievement by one student not only raises his position, but in effect lowers the position of others.
