Depends on the school/uni/college and often the specific lecturer - eg. some teach .NET, some will accept a range of languages. Java has longevity and stability in its favour; and there's consistent demand for it. So it's a sort of "safe bet", which is probably why it's popular.
An ideal course would teach principles and de-emphasise the language used to illustrate it; but reality bites back... it's usually very hard, slow work to get a curriculum updated. Lecturers often just don't have the time to get a range of languages accepted; nor to mark assessment in several different languages. Plus it can be a challenge to prove different students were assessed fairly/equally if they used different languages. Basically academics have a lot to deal with beyond the pure code considerations.
Ultimately there's also some responsibility on the student - if they want to learn something else, learn it! The industry is full of autodidacts who run rings around people who just trudged along a set curriculum.