I'd get myself in shape ... really, really good shape. And I'd probably just abuse it to know all my reading and topic material for my assignments. I mean, I wouldn't do it all that better, I'd just not have to put so much effort into it (also, when I had to debate my teachers to be able to do a topic, I'll know what to expect and just skip to the end, maybe throw in a few mentions that I'm from the future or something. Though, in truth, I'll try to alter the future as minimally as possible, because there are a few people I care for very deeply and I'd hate to screw up all the good work they did over the past two years, especially how much they improved themselves.
So yeah, make a few changes for the sake of simplicity, but other than that I'd maintain my silence for the sake of those I care about.