The goal SAT failed to achieve: upending the hereditary elites and replacing them with meritocratic ones to enhance upper mobility.
Book: The Tyranny of Merit
During early decades of the twentieth century, admission to the Ivy League School depended largely not on academic ability but on whether you are from the right Socioeconomic background. Each college had its own entrance exams, but many people who failed to get a passing grade were nonetheless admitted if they attended one of the private boarding schools that catered to upper-class families or they were children of alumni.
The notion of elite college should recruit and train the most talented students found its most influential articulation by James Bryant Conant, the president of Harvard University in the 1940s. His ambition was to upend the hereditary elites and replace them with meritocratic ones. 
To identify promising students regardless of their family background, Conant insisted that the test for the Harvard Scholarship should measure native intelligence, not mastery of academic subjects, to avoid giving an advantage to those who had attended privileged secondary schools. The test he chose is a version of an IQ test used by the army during World War I which called the Scholastic Aptitude Test (SAT). This test turned out to be not just a way of handing out a few scholarships at Harvard, but the basic mechanism for sorting the American population.
Conant called the term "social mobility" the heart of his argument and used it to define the American ideal of a classless society: "If large numbers of young people can develop their own capacities irrespective of the economic status of their parents, then social mobility is high."
However, as thing turns out, Conant was too sanguine. Making higher education meritocratic did not bring about a classless society. What's worse, it disparaged those excluded for the lack of talent. As Conant later acknowledged, sorting for talent and seeking equality are different. 
 "To be sure, the meaning of merit is fiercely contested. In debates over affirmative action, for example, some argue that counting race and ethnicity as factors in admission violates merit; others reply that the ability to bring distinctive life experiences and perspectives to the classroom and the wider society is a merit relevant to a university’s mission. But the fact that our debates about college admissions are typically arguments about merit testifies to the hold of meritocratic ideals." - Sandel, Michael J. The Tyranny of Merit (p. 163)
 "Conant’s meritocratic vision was egalitarian in the sense that he wanted to open Harvard and other elite universities to the most talented students in the country, however modest their social and economic backgrounds. At a time when Ivy League colleges were dominated by families of established privilege, this was a noble ambition. But Conant was not concerned with expanding access to higher education. He did not want to increase the number of students attending college; he wanted simply to ensure that those who did attend were truly the most capable. In line with this view, he opposed the GI Bill, enacted by FDR in 1944, which provided free college education for returning veterans. The nation did not need more students going to college, Conant thought; it needed better ones." - Sandel, Michael J. The Tyranny of Merit (p. 161)