A lot of the tools that admissions offices use (essays, letters of recommendations) emerged because Harvard, Yale, and Princeton wanted to keep out (or limit the numbers of) the "wrong sort" of people, which, at the time, were Jews, homosexuals, and other such undesirables. Yale even went so far as to have its alumni interviewers comment on the bodies of male applicants. College administrators talked quite openly about the idea that having too many Jews would result in an inferior or degraded college culture.

My source here is Jerome Karabel's book called, naturally, The Chosen.