How do you learn a subject that you already know (like a language)? I have no idea how to approach it for a school class. Any tips?

I'm 100% fluent in Japanese. I was born and lived in Japan for eight years when I was younger and can understand, read, write, and speak it just about as well as anybody who lives in Japan. I have what amounts to a native speaker's accent, and my proficiency (if I may say so myself) is excellent. I've even helped with translating a few works from Japanese to English. I'm actually in a Japanese class right now, which I didn't choose, but my school decided that, as my family *is* from Japan, my elective would be the first Japanese class through AP, and it would then be Japanese History and Culture for my senior year. I've already completed AP Japanese Language and Culture, however, so I have nothing left to do except for take the same class again for the next two years.<br><br>To say I'm bored would be an understatement. I don't really know how to approach the subject, though. In the past, I could study harder and take as many notes as I wanted and learn and move up the grades in a subject. I don't know how to study something that I already know. I've already learned the material. I don't know how to learn something that I know already. What should I do, if anything, to make the class more engaging, or at least to learn something? I'm tired of spending all day playing in the back of the classroom (music) and surfing Chambers (me) and doing the crossword from the local newspaper (another girl whose mom is Japanese). But what should I do to make the class more engaging?<br><br>Any tips would be great.