Hey, Stephan. Welcome to Susan's. Do you live around NYC? If so, Devlyn's list may be of much use to you. I don't know of any place that would do informed consent around here, nor does it sound like your mother would appreciate you going behind her back to get HRT.
Legally changing your name also requires a parent or guardian for minors. You don't need any surgery for that, but you do need to have had surgery in order for your sex to be changed- at least that's how it works in the city. They'll seal off the record of your old birth certificate and give you a new one.
Luckily, you don't need to legally change your name in order to request that others at school call you by your preferred name and pronouns. Or at least that's how NYC is, again. And you need to be 16 for HRT, by the way.
I know how you feel on the issue of parents, but don't give up. My mom completely rejected me when I first came out, and both my parents later decided that it was a phase and that I put it all in my head. They were completely terrible about the whole thing and hurt me a lot, until all of a sudden they changed their minds. I don't know what did it, but they started making small efforts to avoid setting off any further dysphoria. Last night I vented to my mother about trans-related things, and for once she actually listened. It can take days, weeks, months, years...but parents care, and they'll come around in time. Hang in there, kid- your situation is a lot like mine, but things will look up eventually.