How can I fake depression?

Okay so I've been depressed before, and no I am not mocking depression. I think I am bipolar and I'm in a lot of trouble at school, and I'm manic at the moment, so I'm obviously really happy and laughing at everything. I need to get out of trouble and my friend suggested faking depression because they take that seriously. Obviously, if I don't fake it, I will be sitting at the meeting laughing my head off at everything, which I will get expelled for as they won't take me seriously if I say I'm depressed when I look so happy. So what can I do? I need to genuinely look depressed.