In a sense, this is a great advantage of the US society compared to those with traditionally rigid social structures since promotion to upper classes through education opens the way for those from low-income families to move up in their socioeconomic status relatively quickly. With years, however, educational institutions became a tool for sorting school graduates into those who qualify for professional careers and those who do not. Reliance on standardised tests has turned the US system of education into an institution that selects those fitting into the standards and gives them chances for social mobility.
At the same time, the socializing function has become less important. Modern adolescents still seek to make new friends, to have cheerful college years. Their professors remind them that socializing is also important for social mobility, prompting them to build a network of acquaintances that will later contribute to their career. Thus, even socializing has been turned into a vehicle for social mobility. Students increasingly view their educational experience as a step toward career progress rather than a chance to gain friends or broaden their world outlook.
This is visible, for instance, in graduate students aspirations to get into top MBA programs that many see as a gateway to high-salaried executive world. The main advantage of the top programs as compared to the rest, in the eyes of a large part of student body, is that they have sifted through applicants at the beginning, chosen the best ones and sent them off to high posts in business organisations. Socializing takes a second place in these considerations because students are mostly interested in career ambitions and see education as a way to realize them.