Well, if it's a class that is taken just like any other class, by semester, I think it greatly depends on the individual student and their situation. As Bruna M.Nascimento commented, not much is usually said about that student's actual proficiency after the classes are finished, unless some sort of test is administered to ascertain the level. I have personally seen some students who, after taking a language for several years, passed their last test and never attempted to use the language again. :( 

I have also seen others who were highly motivated who studied on their own a great bit, and threw themselves into learning. Many of those students were able to  easily carry on a basic conversation in that language. I think a lot of it depends on people's reasons for learning as well. If it is simply a required course they must take, they don't have a great interest in the language, and don't see that it will be useful for them in the future,  then it's just not always something a student will find themselves passionate about. If it's a language the student really is interested in, they will often retain the information more readily. So, it really depends on the student, and on the teacher sometimes as well, because even if the student is not interested at first, sometimes the teacher can be open and encouraging, and make the class a positive enough experience that the student finds themselves enjoying the experience.