According to the Textbook, Why Are Schools Unsuccessful in Overcoming

According to the textbook, why are schools unsuccessful in overcoming social class differences?

A) because there are differences in intelligence and ability between classes
B) because people are more comfortable remaining with their own class
C) because many extracurricular educational opportunities cost money and are available to people based on ability to pay
D) because many non-middle-class students have difficulty incorporating and appreciating the standards of middle-class, mainstream culture