My school is pretty accepting of me, my guidance counselor even calls me he when she called me down to the office the other day.
Except for the rude stares and comments I get pretty much every day by the same two groups of people, though some people even know that I'm an transgender and know what it means to be so they are pretty respectful and even defend me.
A sophomore last year started the GSA at my school. There are a lot of teachers (including the principal) who attended the meetings and are supportive (most of them know me or have been my teacher at one point). They just now got the courage to make a school announcement about the meeting dates, last year they meet in secret.
I went to two meetings, and I never went back because they focused strictly on LGB issues and not once brought up transgender people. I thought they would at least talk about groups of students who are seen as "different" or have trouble with harassment, but they were strictly LGB. At the last meeting I kind of felt singled out, especially none of my friends showed up so I sat along, so I never went back. In fact, in the announcement that they made, they said something along the lines of "if you are gay, lesbian, bi, or just support LGB, you should attend GSA"
I would attend the meeting, and either talk with the adviser before hand, or when you introduce yourself say that you are a guy, or say what ever you will be comfortable with saying. GSA groups are pretty supportive to how ever attends, they will not single you out or give you a hard time. And since the school has a GSA to begin with, their school has to be somewhat, if not more, supporting of LGBT causes.
I don't think there are any transgender people that are out besides me, but I know of a few people who might be trans, so there's not a whole lot of trans awareness, if anything, there is no awareness at all. Which is really frustrating.