I'm taking two history classes this semester. In at least one of them, the fact that I'm taking my notes in Japanese seems to have become somewhat of an open secret. Although I would have no idea whether or not the professors (of either class) are aware of the situation. It's not something I bothered to hide last semester either, really. In my classes on the two World Wars, I did the same thing, and in those classes the professors did find out.
Simply put, my Japanese is now at the level where simply trying to study disconnected vocabulary and grammar points becomes somewhat pointless. Certainly, I still need to work on my vocabulary, but then that will be true for years to come. At this point, what I need to focus on is using Japanese.
My trip to Japan for study abroad was probably what drove that point home. Prior to leaving for Japan, I was reasonably confident in my Japanese ability, and I was looking forward to using it to get me from the airport to the hotel where my program was gathering. I don't think I had fully accounted for a few things. Like the difference between classroom and reality, or the existence of jet lag, or a number of other problems. And two quick encounters, one at the airport's train station ticket counter and the other in the taxi at Kyoto Station, made it abundantly clear how much harder it is to actually use the language.
This is why I think study abroad is such a powerful boost to language, and why it served that purpose for me. Mastery over a language comes with its constant use, and studying in a country where that language is spoken ensures that you can (and in some cases, must) use it for literally everything. Here in the U.S., that's harder to do. I make up for it by surrounding myself with Japanese as much as possible; all of my music is in Japanese, I watch Japanese anime, I even try to read Japanese books and manga sometimes. But then again, I did that before I left for Japan, too.
Part of that does speak to the necessity of classroom-style learning. Taking someone who knows no Japanese, or very little Japanese, and asking them to process the language anyway only works when the person in question is unusually motivated to learn Japanese, which few people are. Once the base knowledge is there, using the language for anything (including asking about new words or grammar points) becomes important; before that point, doing so usually just sparks confusion at best.
The other half of that, though, suggests that even that isn't enough in the end. Listening to music, watching anime, even reading a book... they're all input. And no matter how much that helps me understand Japanese (which it does), I still need to be able to generate the language as well. So, I take notes in Japanese - because this is the kind of thing I need to be able to do if I want to be able to function entirely in Japanese.