The first adjective one might use to describe Amherst College is “bucolic,’’ or maybe “prestigious.’’ Chances are “diverse’’ doesn’t even crack the top 25. But a decade ago, the school’s “top echelons made an outright decision that it would no longer be a bastion of the white, wealthy elite,’’ says Ilan Stavans, a professor of Latin American and Latino Culture there who has mentored many Latino students. Amherst has since doubled its Latino enrollment from about 6 percent to 12. In 2010, praising its commitment, Hispanic Magazine named it the number five school in the country for Latinos.