First year out of the closet in school tomorrow

Tomorrow I'm going back to high school, this will be my first year out. I'm scared as hell.

I'm in a class of all girls (and apparently they already pity me for being the only guy (they don't know I'm trans)). The thing is I know all of them from other years and they are loud-mouths who really like to pick on people who are outside of the norm.

I know I don't owe them an explanation or something, but they will DEFINITELY be asking because they'll recognize me. I have no idea what to do when they do ask, I want to avoid as much confrontation as possible while making clear I AM a boy.

Is there anything else to say rather than 'Yeah, I'm (name) and I'm a boy now.' Because I know them, they will definitely (for some reason) laugh at me when I say that.