In Jefferson's day, a man was not considered properly educated unless he could read Virgil, Homer, Tacitus, Plutarch and the rest of the classical authors in the original Latin and Greek. The delightful exchange of letters between Jefferson and John Adams in the latter years of their respective lives is filled with charming references in the classical languages, each knowing the other would understand perfectly. These days, however, people who can read Latin and ancient Greek are about as common as chickens with hooves.
Ancient Greek has long been out of reach for everyone except academic specialists, and the days when Latin was required by our schools are long gone as well. Some high schools still offer Latin as an elective course, but they are rare and getting rarer. If we are to recapture Enlightenment values in our own time, this trend should be reversed and schools should be encouraged to offer more widespread education in Latin. Ancient Greek, sadly, is probably out of reach for at least a few generations.
Why would learning classical languages be of any use to anyone, much less any use to society as a whole? First, the ability to read the classics in their original language is not something to be underrated in the slightest. There is more wisdom within the pages of Plutarch and Tacitus, and more beauty within the poetry of Lucretius and Homer, than can be found in any number of modern volumes. I think that if every legislator in every congress or parliament were familiar with Cicero, the quality of our modern political rhetoric would be better by several orders of magnitude. While a vast amount can be gained by reading these works in translation (and several excellent translations exist), it is far better to read them in the original.
Second, learning to read Latin instills rigorous mental discipline in young minds. At a time when they are bombarded with every conceivable kind of distraction, America's young people are increasingly unable to perform even the most basic intellectual tasks, their reading habits are pathetic when compared to earlier generations, and their attention spans raise alarm even among the most optimistic education specialists.
Also, because English and most foreign languages Americans routinely encountered are, at least in large part, derived from Latin, a working knowledge of Latin gives a young person a "leg up" when they encountered unfamiliar terms in fields ranging from botany and biology to medicine and law. Learning Latin helps a young person understand the subtleties of his or her own language. Indeed, Latin permeates our culture in ways so basic that the average person is utterly unaware of it.
The values and virtues of classical civilization still existed in the 18th Century and the fact that educated persons could read and write in both Latin and Greek was a major reason why. In our time, we have divorced ourselves utterly from classical civilization, and there is much that we need to recover. A good place to start would be a restoration of a widespread knowledge of Latin among our students.