This might be too broad of a question, but it is something I've wondered for a while. Was there a time when most universities changed to instructing in local languages or was a it a gradual process? Was there a huge movement in the reformation? The enlightenment? Under the influence of 19the century nationalism? Even later? I know that a huge part of medieval education was to gain competence in Latin in order to engage in the intellectual life.
I see that, for example, Wittenberg moved to German in the 18the century, but Charles University in Prague didn't shift to Czech and German until the 19the century.
Did certain areas like England make the shift far earlier? I know many Scottish nd English students pursued degrees in, e.g. Leiden in the 17th century. Would that necessitate the education being in Latin? Likewise, did any of the earliest American universities like Harvard ever use it as their medium of education? Thanks for your help and sorry if this has been addressed in other threads. A search did not reveal any dealing with it.
This is a really big question and it's not my particular specialty but I did take a course on the history of American Universities, so I feel like I might be able to address a small fragment of the question at hand.
Yes, American universities did start off with Latin instruction. They very much modeled themselves after the English universities, Cambridge and Oxford. These universities often taught with the Trivium at the forefront (Grammar, Logic, and Rhetoric). According to Edward Kennard Rand in The New England Quarterly (1933), the program at Harvard was divided into the Theses Philologicae (i.e. the Trivium) and These Philosophicae (ethics, physics, and metaphysics).
Latin was an integral part of the education mostly because it was necessary to know the language. Knowledge of Greek and Hebrew was also needed. Quoting Rand:
The languages (Greek, Latin, and Hebrew) were not studied as mere exercises in parsing or translating. The utility of the study of languages is emphasized and the general character of each language was discussed, according to the fashion of the day.
To make a long story short, the issue of teaching with classical languages became a big argument among the universities and colleges in America. The use of vernacular languages rose with the desire to study more practical subjects (i.e. science). The major document that historians reference this argument to for American Universities is the Yale Report of 1828. One paragraph in it highlights some of the arguments for/against the shift in using historical European languages vs modern languages (i.e. English, German, Italian, etc.)
Modern languages, with most of our students, are studied, and will continue to be studied, as an accomplishment, rather than as a necessary acquisition. .... To suppose the modern languages more practical than the ancient, to the great body of our students, because the former is now spoken in some parts of the world, is an obvious fallacy. The proper question is,--what course of discipline affords the best mental culture, leads to the most thorough knowledge of our own literature, and lays the best foundation for professional study. The ancient languages have here a decided advantage. If the elements of modern languages are acquired by our students in connection with the established collegiate course, and abundant facilities for this purpose, have for a long time, been afforded, further acquisitions will be easily made, where circumstances render them important and useful. From the graduates of this college, who have visited Europe, complaints have sometimes been heard, that their classical attainments were too small for the literature of the old world; but none are recollected to have expressed regret, that they had cultivated ancient learning while here, however much time they might have devoted to this subject. On the contrary, those who have excelled in classical literature, and have likewise acquired a competent knowledge of some one modern European language besides the English, have found themselves the best qualified to make a full use of their new advantages. Deficiencies in modern literature are easily and rapidly supplied, where the mind has had a proper previous discipline; deficiencies in ancient literature are supplied tardily, and inmost instances, imperfectly ....
Anyway, eventually as practical studies picked up, you see the argument for classical languages wane. So your question is definitely an interesting one because it definitely plays into the larger question of what the role of college was. By moving from Latin to vernacular languages, your seeing the beginning of a shift from "colleges as tickets to elite status/civic positions/etc." to "colleges with a broader education goal"
There are likely people more qualified to answer this question, but hopefully this starts the discussion :) I really really enjoyed Frederick Rudolph's The American College and University: A History (1962) which dives into some of these issues early on in the book.