Kemp Mill Synagogue is a spiritual home to lobbyists, policy scholars, and White House staffers. It looks out over the opening of a lushly wooded forest valley in suburban Maryland, just down the street from a horse farm. One of its common nicknames used to be Congregation Bnei Ivy—the people of the Ivy League. The name alludes to an enduring way of life for an influential segment of American Jews. The eight Ivy League schools are a collective stand-in for the meritocratic system that turned the children and grandchildren of penniless Yiddish-speakers into some of the richest and most important...