Mixed up with the question of fairness to individuals and groups has been the explosive question of whether individuals and groups have the innate ability to perform at the same levels, if they are all treated alike or even given the same objective opportunities.
Intellectuals have swung from one side of this question at the beginning of the 20th century to the opposite side at the end. Both those who said that achievement differences among races and classes were due to genes, in the early years of the 20th century, and those who said that these differences were due to discrimination, in the later years, ignored the old statisticians' warnings that correlation is not causation.
The idea that some people are innately superior (usually one's own group) goes back for centuries, but various new facts that came out in the 19th and early 20th centuries gave the appearance of "science" to such beliefs during the Progressive era.
Sir Francis Galton's research turned up the fact of remarkable achievements among members of the same family, which he regarded as evidence of genetic superiority. The rise of IQ testing, and especially the massive mental testing of soldiers in the U.S. Army during the First World War, showed great differences in test scores among various racial and ethnic groups.
In the public schools, there were similarly large differences in which ethnic group's children failed to get promoted. In both the Army mental tests and in the schools, Polish Jews did poorly at that time. Carl Brigham-- a leading authority on mental tests and the author of the SAT-- said that the Army tests tended to "disprove the popular belief that the Jew is highly intelligent."
It should be noted that all of these conclusions were based on hard data, not mere "perceptions" or "stereotypes," as so many inconvenient facts are dismissed today. What was wrong were not the data but the inferences.
Polish Jews were among the many immigrants from Eastern Europe and Southern Europe who were relatively recent arrivals in the United States. Many of these immigrants grew up in homes where English was not spoken, as Carl Brigham acknowledged in later years, when he recanted his earlier statements. In later years, Jews scored above average on mental tests.