Do not try to live as male if you can't pass. Trust me, people get weirded out by these sorts of things. You can come across as a tomboy if anything, but don't try to go male until you are certain you can pass. It may be tempting, but think about it first. What would a bunch of guys do if they saw a girl in their bathroom or locker room? What if a guy went into the girl's bathroom? The point is, you'll get in trouble and labeled as some perv and//or slut. Just let things slide until you start HRT. Once you're ready to go full time, tell all of your teachers that you're trans and that you want to be treated as male. They'll likely make an announcement to the students. That's what happened in my school. Most importantly, don't just drop in presenting as male without some warning. People might be taken aback.
I would say you can change your name and dress in a guy-ish manner, but that's it. All I saw was "conservative", so I'd say be cautious in this place. I must say that Robert does make a good point, if guys saw a girl in their locker rooms, they might actually like it, but it's better to be safe than sorry.